Chapter 7 Atomic Nucleus Topic A Radioactivity Synopsis:
1. Radioactive elements are those elements whose atoms spontaneously emit a type of special invisible radiation and get converted into atoms of new elements.
2. Radioactivity was discovered by Henri Becquerel in uranium salt in the year 1896.
3. Radioactivity is the property due to which some elements with high atomic mass numbers spontaneously emit a type of special invisible radiation and get converted into atoms of new elements.
4. All the elements with atomic numbers greater than 82 are naturally radioactive.
5. Some non-radioactive elements may be converted into radioactive elements artificially. The radioactivity of these new elements produced artificially is called artificial radioactivity.
6. The phenomenon of spontaneous emission of rays from an unstable nucleus is called
radioactive decay.
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7. radioactive element or atom that exhibits radioactivity is called a parent atom. The atom that is left behind after the emission of radioactive radiation is called the daughter atom.
8. No radioactive sample can emit all three radiations simultaneously.
Wbbse Class 10 Physical Science Solutions
8. Three types of rays are emitted in radioactivity.
α – ray: It is a stream of positively charged particles.
β – ray: It is a stream of negatively charged particles.
γ – ray: It is an electromagnetic wave.
9. Charge of an or α-particle is twice the charge of a proton, its symbol is \({ }_2^4 \mathrm{He}\), mass is 6.642 x10-27 kg (or 4.0015 u).
10. Charge of a β-particle is equal to the charge of an electron, i.e., -1.6 x 10-19 C. Its symbol is \({ }_{-1}^0 \beta,\) mass is 9.1 x 10-31 kg.
11. If an atomic nucleus undergoes α-decay, the atom is transformed into an atom with a mass number that is reduced by four units and an atomic number that is reduced by two units.
\(
{ }_Z^A X \longrightarrow{ }_{Z-2}^{A-4} Y+{ }_2^4 \mathrm{He}
\)
(parent) (daughter)
12. If an atomic nucleus undergoes β-decay, the atom is transformed into another atom whose mass number remains unchanged, and the atomic number increases by one unit.
\(
{ }_Z^A p \longrightarrow{ }_{Z+1}^A Q+{ }_{-1}^0 e
\)
(parent) (daughter)
Wbbse Class 10 Physical Science Solutions
13. If γ-ray is emitted from a nucleus, the mass number and an atomic number of the atom remain unchanged.
14. Radioactive isotopes are used for the treatment of cancer, leukemia, and diseases of the thyroid. In addition, the radioisotope of carbon 14C is used for determining the age of a fossil or archaeological object.
Chapter 7 Atomic Nucleus Topic A Radioactivity Short And Long Answer Type Questions:
Question 1. What is radioactivity? Which: eSemerit does show radioactivity?
Answer:
Radioactivity:
1. Radioactivity is the property due to which some elements with high atomic mass numbers spontaneously emit a type of special invisible radiation and get converted into atoms of new elements.
2. In Elements in which the ratio of neutrons and protons in the nuclei is more than 1.5, the nuclei are unstable. These elements emit radioactive radiation spontaneously and try to become stable. Only that element shows radioactivity whose mass number is 210 or more than that.
Question 2. What are the characteristics of radioactivity?
Answer:
The characteristics of radioactivity are:
1. Radioactive rays emit spontaneously and ceaselessly from a radioactive element.
2. No effect does occur in the emission of radioactive rays even in the application of heat, pressure, light, electric field, or magnetic field on the radioactive substance.
3. If radioactive elements undergo a chemical change and form other compounds, there is no change in their radioactive nature.
4. Radioactivity of an element is a phenomenon fully associated with its nucleus, there is no connection with its electronic configuration.
5. Structure of the nucleus changes as a result of the emission of radioactive rays. In other words, the numbers of protons and neutrons in the nucleus change, and as a result, a new element is formed.
Question 3. Write down three characteristics of radioactive radiation.
Answer:
Characteristics of radioactive radiation:
1. The radiation has a high penetrating power. For example, gamma rays require a 1 cm thick lead slab to reduce their intensity by 50%.
2. Radioactive rays can ionize a gas.
3. This radiation affects the photographic plates.
Wbbse Class 10 Physical Science Solutions
Question 4. What is artificial radioactivity? Name three artificial radioactive elements.
Answer:
Artificial radioactivity:
1. Some non-radioactive elements may be converted into radioactive elements artificially. The radioactivity of these new elements produced artificially is called artificial radioactivity.
2. Three artificial radioactive elements are
Question 5. Radioactivity of any element is completely a nuclear phenomenon-explain?
Answer:
Radioactivity of any element is completely a nuclear phenomenon:
1. The property of radioactivity of radioactive elements remains unchanged even when they form other compounds after their chemical change. For example, radium chloride, a compound of radioactive radium, is also radioactive.
2. The chemical properties of an element depend on the electronic configuration in its different orbits. As the radioactivity of a radioactive element remains present after chemical changes, so there is no relation between radioactivity and the electronic configuration of the element.
3. Furthermore, an element with new properties is formed as a result of the emission of radioactive rays. This is possible only if there is a change in the structure of the nucleus, i.e., a change in the number of neutrons and protons in the nucleus. This is why it is said that the radioactivity of any element is completely a nuclear phenomenon.
Question 6. Define parent atom and daughter atom. What is the position of a daughter atom in the periodic table when one a -particle is emitted from the nucleus of a radioactive element? What is the position of a daughter atom in the periodic table when one β-particle is emitted from the nucleus of a radioactive element?
Answer:
1. Parent atom of the radioactive element is that atom that undergoes radioactive decay. The atom of the new element which is produced after the emission of the radioactive rays is called the daughter atom.
2. If one α-particle is emitted from the nucleus of a radioactive element, the atomic number of the daughter atom is reduced by two units. So the daughter element moves 2 places to the left in the periodic table compared to the parent atom.
3. If one β-particle is emitted from the nucleus of a radioactive element, the atomic number of the daughter atom is increased by one unit. So the daughter element moves 1 place to the right in the periodic table compared to the parent atom.
Wbbse Class 10 Physical Science Solutions
Question 7. Compare α-ray, β-ray, and γ-ray on the basis of their masses.
Answer:
Comparison among α-ray, β-ray, and γ-ray on the basis of their masses is discussed below:
| α-ray | β-ray | γ-ray |
| The mass of one α-ray-particle is nearly 4 times greater than the mass of a proton. Its mass is 6.642 X 1027 kg. | The mass of one β-ray particle is nearly equal to the mass of an electron or 9.1 x 10-31 kg. | γ-ray is a type of electromagnetic radiation signifying that its mass is zero. |
Question 8. Compare α-ray, β-ray, and γ-ray on the basis of their charges.
Answer:
Comparison among α-ray, β-ray, and γ-ray on the basis of their charges discussed below:
| α-ray | β-ray | γ-ray |
| α-ray is a stream of positively charged particles. The nature ofα-ray particle is similar to that of a helium ion (He2+) with 2 units of positive charge. The charge of an a-particle is 3.2 x 10-19 C. It is twice the charge of a proton. | β-ray is a stream of negatively charged particles. The charge of a β-ray particle is equal to the charge of an electron i.e., -1.6 x 10-19 C. | γ-ray is a type of electromagnetic wave with a small wavelength. This is not the stream of any particle. γ-ray is electrically neutral. |
Question 9. Compare α-ray, β-ray-ray, and γ-ray on the basis of their penetrating power.
Answer:
Comparison among α-ray, β-ray, and γ-ray on the basis of their penetrating power discussed below:
| α-ray | β-ray | γ-ray |
| α-ray has less penetrating power than β-ray and γ-ray In practice, after progressing a few centimeters through the air, an α-ray particle becomes motionless. | The penetrating power of β-ray is greater than that of α-ray but less than that of γ-ray. An aluminum foil of 5 mm thickness can stop β-ray. | The penetrating power of γ-ray is many times more than those of α-ray and β-ray. γ-ray can penetrate an aluminum sheet of thickness 100 cm. |
Question 10. Compare α-ray, β-ray, and γ-ray on basis of their ionising power.
Answer:
Comparison among α-ray, β-ray, and γ-ray on the basis of their ionising power discussed below:
| α-ray | β-ray | γ-ray |
| α-ray has the maximum power to ionise gases. The ratio of power to ionise gases of α, β and γ-rays is 10000: 100 :1 | β-ray has more power to ionise gases than γ-ray but less than that of α -ray. | γ-ray has less power to ionise gases than α-ray and β-ray. |
Question 11. How does the nucleus of a radioactive atom change after the emission of an α-particle? Radium ( \({ }_{88}^{226} Ra\)) is converted into radon (Rn) by emission of one α-particle. Calculate the mass number and an atomic number of radon.
Answer:
1. If an α-particle is emitted from the nucleus of a radioactive atom, a new nucleus is formed whose mass number is reduced by 4 units and atomic number is reduced by 2 units.
\({ }_Z^A \mathrm{X} \stackrel{-\alpha \text {-particle }}{\longrightarrow}{ }_{Z-2}^{A-4} Y\)
(parent atom) (daughter atom)
2. In this case, mass number of radon = 226-4 = 222 and atomic number = 88 – 2 = 86
Wbbse Class 10 Physical Science Solutions
Question 12. What is the ratio of masses of an α- particle and β-particle which are emitted from a radioactive atom? There is no electron in the nucleus of an atom. Then how is an electron emitted as a β-particle from atom of a radioactive element?
Answer: Mass of an α-particle/ Mass of a β-particle
= \(\frac{\text { mass of four protons (approx.) }}{\text { mass of one electron }}\)
= \(\frac{4 \times 1.6605 \times 10^{-27} \mathrm{~kg}}{9.1 \times 10^{-31} \mathrm{~kg}}\)
= 0.7299 x 104 = 7299 (approx.)
In the phenomenon of emission of a (β -particle from the nucleus of a radioactive atom, a neutron (n) is disintegrated to produce one proton (p) and one electron (e). The produced proton remains within the nucleus and the electron comes out of the nucleus with a very high velocity. This is the reason why an electron is emitted as a β-particle from the atom of a radioactive element, in spite of the fact that there is no electron in the nucleus.
Question 13. How does the nucleus of a radioactive atom change after emission of a β-particle? Thorium (\({ }_{90}^{234} Th\)) is converted into protactinium (Pa) by emission of one β particle. Calculate the mass number and atomic number of protactinium.
Answer: If a β-particle is emitted from the nucleus of a radioactive atom, a new nucleus is formed whose mass number remains unchanged but the atomic number increases by one unit.
\({ }_Z^A X \stackrel{-\beta \text {-particle }}{\longrightarrow}{ }_{Z+1}^A Y\)
(parent atom) (daughter atom)
In this case, mass number of protactinium = 234 and atomic number = 90 + 1 = 91
Wbbse Class 10 Physical Science Solutions
Question 14. What is the ratio of charges of α-particle and β-particle? Why is lead present in the mineral of any radioactive metal?
Answer: Charge of α-particle / Charge of β-particle
= \(\frac{\text { charge of } 2 \text { protons }}{\text { charge of } 1 \text { electron }}\)
[∴ charge of 1 proton = charge of 1 electron]
Due to successive radioactive emissions from any radioactive element, it is ultimately converted into a non-radioactive isotope of lead (82Pb). After this, there is no further radioactive decay. This is why lead is available in the mineral of any radioactive metal.
Question 15. Write down the differences between an β-particle and an ordinary electron?
Answer: Differences between an β-particle and an ordinary electron:
| β-particle | Ordinary electron |
| 1. β-particle is emitted instantaneously after its creation in the nucleus of a radioactive atom. | 1. Ordinary electrons remain in different orbits outside the nucleus of the atom. |
| 2. After the emission of an β-particle from the nucleus of a radioactive element, the mass number of the new element remains the same but the atomic number increases by one unit. | 2. An atom is converted into a positively charged ion after the emission of an ordinary electron from the atom. |
Question 16. Write down the differences between a radioactive change and a chemical change.
Answer: The differences between a radioactive change and a chemical change:
| Radioactive change | Chemical change |
| 1. Radioactive change is a nuclear phenomenon | 1. Chemical change is a phenomenon involving valence electrons in the orbits of the atom. |
| 2. Radioactive change is not influenced by external pressure, light, catalyst, electric field or magnetic field. | 2. Chemical change is influenced by external pressure, light, catalyst etc. |
| 3. Radioactive change is a irreversible change. | 3. Chemical change may be irreversible as well as reversible. |
| 4. A new element is- formed in a radioactive change. | 4. No news element is formed in a chemical change. |
| 5. Huge amount of energy is produced in a radioactive change. | 5. Amount of energy produced in a chemical change is less than that produced in a radioactive change. Moreover in some cases, energy is absorbed in a chemical change. |
Question 17. An an α-particle is emitted from a nucleus X in the following way: \({ }_{92}^A X \longrightarrow \frac{228}{z} Y+\alpha\). Calculate the values of A and Z from the above reaction. Why is helium gas available in the mines of some radioactive metals?
Answer:
1. The new atom that is formed from the radioactive nucleus after emission of an α-particle gets its mass number and atomic number reduced by 4 units and 2 units, respectively.
A = 228+4 = 232 and Z= 92-2 = 90
2. α-particle that emits from a radioactive element in a mine of radioactive metals ionises the gas. The α-particle is converted into a helium atom by acquiring 2 electrons from the surroundings and remains inside the mine as helium gas.
Wb Class 10 Physical Science Question and Answers
Question 18. Mention three applications of radioactivity
Answer:
Applications of radioactivity:
Radioactive elements are used at present in many areas including medical science.
1. Radioactive elements radium, cobalt ( 60Co) are used to destroy those cells which are affected by cancer. Radioactive phosphorus (32P) is used for the treatment of leukemia and brain tumour. Radioactive iodine (131I) is used for the treatment of the disease of the thyroid.
2. Radioactive elements are used to determine the suitability of certain raw materials used in different industrial units.
3. A smoke detector has been manufactured on the basis of a special characteristic of the radioactive material {americium-241). This instrument can detect smoke which is emitted due to an accidental fire, and alarm the people by the sound of a siren.
Question 19. What is the mass number and atomic number of the new elementary particle that is produced when 8 α-particles and 6 β-particles are emitted successively (one after another) from the nucleus of \({ }_{92}^{238} U\)?
Answer: If one α-particle is emitted from the nucleus of any radioactive element, its mass number is reduced by 4 units and its atomic number is reduced by 2 units. If one β-particle is emitted, the mass number remains unchanged but the atomic number increases by 1 unit.
Since 8 α-particles and 6 β-particles are emitted 238 from the nucleus of \({ }_{92}^{238} U\), the mass number of the new element = 238 – (4 x 8) = 206 and atomic number = 92 – (2 x 8) + (1 x 6) = 92 – 16 + 6 + 82
Chapter 7 Atomic Nucleus Topic A Radioactivity Very Short Answer Type Questions Choose The Correct Answer:
Question 1. Among the following rays, which one has the maximum power to ionise gases?
1. α
2. β
3. γ
4. Visible ray
Answer: 1. α
Question 2. Among the following rays, which one has the maximum penetrating power?
1. α
2. β
3. γ
4. Visible ray
Answer: 3. γ
Question 3. Among the following isotopes, which one is radioactive?
1.12C
2. 14C
3. 16O
4. 23Na
Answer: 2. 14C
Question 4. Speed of γ – ray in vacuum is
1. 2 x 108 m/s
2. 3 x 108 m/s
3. 1.5 x 108 m/s
4. 2.5 x 108 m/s
Answer: 2. 3 x 108 m/s
Question 5. Charge of an a-particle is
1. 1.6 x 10-19 C
2. 3.2 x 10-19 C
3. 4.8 x 10-19 C
4. 6.4 x 10-19 C
Answer: 2. 3.2 x 10-19 C
Wb Class 10 Physical Science Question and Answers
Question 6. What is the mass of a β-particle, if the mass of an electron is m?
1. m
2. 2m
3. 3m
4. 4m
Answer: 1. m
Question 7. Which of the following is used determination of the age of fossils?
1. 60Co
2. 131I
3. 32P
4. 14C
Answer: 4. 14C
Question 8. Who discovered radioactivity?
1. Ernest Rutherford
2. Madame Curie
3. Pierre Curie
4. Henry Becquerel
Answer: 4. Henry Becquerel
Question 9. If a powerful static electric field is applied in a perpendicular direction to the path of radioactive rays, which ray does bend towards the positively charged terminal?
1. α
2. β
3. γ
4. None of these
Answer: 2. β
Wb Class 10 Physical Science Question and Answers
Question 10. If a powerful static electric field is applied in a perpendicular direction to the path of radioactive rays, which ray. does bend towards the negatively charged terminal?
1. α
2. β
3. γ
4. None of these
Answer: 1. α
Question 11. The value of e/m of an α-particle is m of that of an ionised hydrogen.
1. Two times
2. Four times
3. Half
4. Equal
Answer: 3. Half
Question 12. If a powerful static electric field is applied in a perpendicular direction to the path of radioactive rays, which ray does not deviate?
1. α
2. β
3. γ
4. None of these
Answer: 3. γ
Question 13. The particle that escapes when β-decay (\({ }_{-1}^0 \mathrm{e}\)) takes place from the nucleus of an atom is
1. Neutrino
2. Antineutrino
3. Meson
4. Positron
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Answer: 2. Antineutrino
Question 14. The new nucleus that is formed due to β- the decay of the nucleus of a \({ }_6^{14} \mathrm{C}\) atom is
1. \({ }_6^{13} \mathrm{C}\)
2. \({ }_7^{14} \mathrm{~N}\)
3. \({ }_5^{14} \mathrm{~B}\)
4. \({ }_8^{14} \mathrm{O}\)
Answer: \({ }_6^{13} \mathrm{C}\)
Question 15. Which of the following has a speed equal to that of light?
1. α-ray
2. β-ray
3. γ-ray
4. None of these
Answer: 3. γ-ray
Question 16. If an α-particle is emitted from the nucleus of \({ }_Z^A X\) atom thereby producing Y element, then the mass number and atomic number of Y are
1. A,2-2
2. A – 2, Z — 2
3. A – 4, Z- 2
4. 4-4, Z
Answer: 3. A – 4, Z- 2
Question 17. If a β-particle is emitted from the nucleus of \({ }_Z^A X\)atom thereby producing Y element, then the mass number and atomic number of Y are
1. A, Z
2. A+ 1,Z+l
3. A, Z + 1
4. A-1, Z-l
Answer: 3. A, Z + 1
Question 18. How many αparticles in succession to one α particle need to be emitted from the nucleus of an atom of X to make the new element an isotope of X?
1. 1
2. 2
3. 3
4. 4
Answer: 2. 2
Question 19. Which of the following is not radioactive?
1. 32P
2. 14C
3. 40K
4. 23Na
Answer: 4. 23Na
Question 20. If m is the mass of an electron, then the mass of a positron is
1. m
2. m/2
3. 2m
4. 4m
Answer: 1. m
Wb Class 10 Physical Science Question and Answers
Question 21. Particles that can be added to the nucleus of an atom without changing its chemical properties are
1. Neutrons
2. Electrons
3. Protons
4. Positrons
Answer: 1. Neutrons
Question 22. Which of the following particles are constituents of the nucleus?
1. Protons and electrons
2. Neutrons and electrons
3. Electrons and positrons
4. Neutrons and protons
Answer: 4. Neutrons and protons
Question 23. The mother and daughter elements with the emission of β-rays are
1. Isotopes
2. Isobars
3. Isomers
4. Isodiaphers
Answer: 2. Isobars
Question 24. The mother and daughter elements with the emission of γ-rays are
1. Isotopes
2. Isobars
3. Isomers
4. Isodiaphers
Answer: 3. Isomers
Question 25. The nuclei of \({ }_6^{13} \mathrm{C}\) and \({ }_7^{14} \mathrm{~N}\) can be described as
1. Isodiaphers
2. Isotones
3. Isobars
4. Isotopes
Answer: 2. Isotones
Question 26. 1 Curie is
1. 1 dps
2. 3 Χ1010 dps
3. 3.7 Χ1010 dps
4. 106 dps
Answer: 3. 3.7 Χ1010 dps
Question 27. In \({ }_{88}^{226} R\) nucleus, there are
1. 138 protons and 88 neutrons
2. 138 neutrons and 88 protons
3. 226 protons and 88 electrons
4. 226 neutrons and 138 electrons
Answer: 2. 138 neutrons and 88 protons
Question 28. An atomic number of a nucleus is 2 and its atomic mass is M. The number of neutrons is
1. M-Z
2. M
3. Z
4. M + Z
Answer: 1. M-Z
Wb Class 10 Physical Science Question and Answers
Chapter 7 Atomic Nucleus Topic A Radioactivity Answer In Brief:
Question 1. α-ray is composed of which type of electrically charged particles?
Answer: α-ray is composed of positively charged particles.
Question 2. β-ray is composed of which type of electrically charged particles?
Answer: β-ray is composed of negatively charged particles.
Question 3. Among α-ray, β-ray, and γ-rays, which one is electrically neutral?
Answer: γ-ray is electrically neutral.
Question 4. Is α-ray scattered by an electric field?
Answer: Yes, α-ray is scattered by an electric field.
Question 5. What are radioactive elements?
Answer: Radioactive elements are those elements whose atoms spontaneously emit a type of special invisible radiation and get converted into atoms of new elements.
Question 6. Write down the names of three natural radioactive elements.
Answer: Polonium (Po), radium (Ra) and uranium (U) are three natural radioactive elements.
Question 7. Write down the names of two radioactive elements whose Z < 20.
Answer: \({ }_6^{14} \mathrm{C}\) and \({ }_6^{14} C\) are two radioactive elements whose Z < 20.
Question 8. In between \({ }_6^{12} C\) and \({ }_6^{14} \mathrm{C}\), which one is radioactive?
Answer: \({ }_6^{14} \mathrm{C}\) is radioactive.
Question 9. Arrange the following rays according to the descending order of penetrating power: α-ray/ β-ray,γ-ray.
Answer: α-ray>β-ray>γ-ray
Wb Class 10 Physical Science Question and Answers
Question 10. Arrange the following rays according to the ascending order of power to ionise gases: α-ray/ β-ray,γ-ray.
Answer: α-ray<β-ray<γ-ray
Question 11. Write down the name of an instrument that measures radioactivity.
Answer: G-M Counter (Geiger-Muller Counter) measures radioactivity.
Question 12. Which element is responsible for the radioactivity of potassium uranyl sulphate?
Answer: Uranium is responsible for the radioactivity of potassium uranyl sulphate.
Question 13. What is the effect of radioactivity on the cells of a living organism?
Answer: The effect of radioactive rays on a cell may be fatal as it may destroy active cells.
Question 14. How many protons in the nucleus are reduced if one α-particle is emitted from the nucleus of a radioactive element?
Answer: Two protons are reduced in the nucleus if one α-particle is emitted from the nucleus of a radioactive element.
Question 15. How many neutrons in the nucleus are reduced if one α-particle is emitted from the nucleus of a radioactive element?
Answer: Two neutrons are reduced in the nucleus if one α-particle is emitted from the nucleus of a radioactive element.
Question 16. How many types of ray are emitted from a radioactive substance? Write down their names.
Answer: Three types of ray are emitted from a radioactive substance, namely alpha (α) ray, beta (β) ray, and gamma (γ) ray.
Physical Science Class 10 West Bengal Board
Question 17. Among the rays which are emitted from a radioactive material, which is an electromagnetic wave?
Answer: Among the rays which are emitted from a radioactive material, a gamma ray is an electromagnetic wave.
Question 18. Of all the rays emitted from a radioactive material, which rays have particle nature?
Answer: Of all the rays emitted from radioactive material, α-ray and β-ray are streams of particles with masses and thus, have a particle nature.
Question 19. Which is massless among α, β, and γ-rays?
Answer: γ-ray is massless.
Question 20. Where does radioactive change take place inside an atom?
Answer: Radioactive change takes place in the nucleus of the atom.
Question 21. Is a radioactive change unidirectional or bidirectional?
Answer: A radioactive change is always unidirectional.
Question 22. A compound of a radioactive element is formed a chemical reaction. Is there any change does occur in radioactivity?
Answer: Radioactivity remains unchanged even if a compound of a radioactive element is formed in a chemical reaction.
Question 23 A is a radioactive element. A is converted to element B by emitting successively one α-particle and two β-particles. What is the relation between A and B?
Answer: If the atomic number of element A is Z, then the atomic number of element B becomes Z-2 + 1 + 1-Z.
∴ A and B are isotopes of each other.
Physical Science Class 10 West Bengal Board
Question 24. What is the SI unit of radioactivity?
Answer: SI unit of radioactivity is becquerel (Bq).
Question 25. The atomic number is not changed by which type of radioactive decay?
Answer: γ – decay.
Question 26. Helium ions and α-particles are the same or different?
Answer: Helium ions and α-particles are the same.
Question 27. What type of radioactive decay is caused when there are too many neutrons in the nucleus?
Answer: β-decay.
Question 28. Which part of an atom undergoes a change in the process of radioactive decay?
Answer: The nucleus of an atom undergoes a change in the process of radioactive decay.
Question 29. Name the radioactive radiation which have the least penetrating power.
Answer: ‘α’-radiation have the least penetrating power.
Physical Science Class 10 West Bengal Board
Question 30. A radioactive substance is oxidised. What change takes place in the nature of radioactivity?
Answer: No change takes place.
Question 31. Name the positively charged particle that emanates from an uranium nucleus.
Answer: The positively charged particles that emanate from an uranium nucleus is ‘α’- particle.
Question 32. Name a negatively charged radioactive – particle.
Answer: A negatively charged radioactive particle is β-particle.
Question 33. Why are emissions of α-particles, β-particles, and γ-rays called nuclear phenomenon?
Answer: These emissions are entirely nuclear phenomenon because that happens due to internal changes in the nucleus.
Physical Science Class 10 West Bengal Board
Chapter 7 Atomic Nucleus Topic A Radioactivity Fill In The Blanks:
Question 1. After emission of one _______ particle, \({ }_{13}^{28} \mathrm{Al}\) is transformed into \({ }_{14}^{28} \mathrm{Si}\).
Answer: β
Question 2. γ-ray is a type of ______ wave.
Answer: Electromagnetic
Question 3. The atom of the radioactive element which undergoes radioactive decay is called ______ atom.
Answer: Parent
Question 4. The atom of the new element that is produced after emission of a radioactive ray from the nucleus is called a ______ atom.
Answer: Daughter
Question 5. The rest mass of γ-ray is ______.
Answer: Zero.
Question 6. The age of a fossil and an archaeological object is determined by measuring the ratio of _______ and 12C in it.
Answer: 14C.
Question 7. The charge of an α-particle is_______ of that of a hydrogen ion.
Answer: Twice
Question 8. If an α-ray falls on a screen coated with zinc sulfide, it creates ______.
Answer: Fluorescence
Question 9. α-particle is the nucleus of a atom.
Answer: Helium
Physical Science Class 10 West Bengal Board
Question 10. Atomic number of a radioactive nucleus is not affected due to emission of ______ ray from it.
Answer: γ
Question 11. Charge of the positron is ______.
Answer: +1.6 10-19 C
Question 12. Radioactivity is totally a ______ phenomenon.
Answer: Nuclear
Question 13. When a radioactive element emits one alpha particle, its atomic no ______ by 2 and mass number ______ by 4.
Answer: Decreases and Decreases
Question 14. The radioactive, nature of two uranium isotopes \({ }_{92}^{235} U\) and \({ }_{92}^{238} U\) are ______.
Answer: Different.
Question 15. When a radioactive element emits one ______ particle, its atomic number increases by 1.
Answer: β
Wbbse Class 10 Physical Science Chapter 7 Question And Answers
Question 16. 131I isotope is used to test the activity of ______ gland.
Answer: Thyroid
Chapter 7 Atomic Nucleus Topic A Radioactivity State Whether True Or False:
Question 1. Nucleon is a collective name for two particles, the neutron, and proton.
Answer: True
Question 2. An electron has a greater mass than a proton.
Answer: False
Question 3. When an or-particle is ejected, the atomic number of the atom decreases by 2.
Answer: True
Question 4. β-ray has the highest penetrating power.
Answer: False
Question 5. Isotopes are the atoms having same atomic number but different mass number.
Answer: False
Question 6. β-rays and cathode rays are identical in nature.
Answer: True
Question 7. No radioactive sample can emit all three radiations α, β and γ-simultaneously.
Answer: True
Question 8. γ rays can be completely absorbed in 1/10mm thick aluminum plate.
Answer: False
Chapter 7 Atomic Nucleus Topic B Nuclear Energy Synopsis:
1. The mass of a nucleus is slightly less than the mass of the sum of protons and neutrons present in the nucleus. This difference between the two masses is called the mass defect(Δm).
The atomic number and the mass number of the atom are Z and A respectively. If the masses of the proton and the neutron are mp and mn respectively and the mass of the nucleus of the atom is M, then mass defect, \(\Delta m=Z \cdot m_p+(A-Z) m_n-M\).
2. Binding energy is defined as the minimum energy required to disassemble a nucleus of an atom into its constituent particles. It is the equivalent amount of energy of mass defect.
Wbbse Class 10 Physical Science Chapter 7 Question And Answers
If Δm is mass defect then according to Einstein’s mass-energy relation binding energy =Δmc2
3. Binding energy per nucleon is the average energy required to release a nucleon from the nucleus. Binding energy per nucleon ∝ stability of the nucleus.
4. The Einstein equivalent of mass and energy can be stated as: If the mass m of a body is completely converted to energy, then the measure of the energy is
E=mc2, c = speed of light in vacuum.
5. Unified atomic mass unit: 1/12th of the mass of a 12C atom is called 1 amu or 1 u.
∴ \(1 \mathrm{u}=\frac{1}{12} \times \frac{12}{6.022^{\prime} \times 10^{23}} \mathrm{~g}\)= 1.6605 x 10-27 kg
6. If 1 u mass is completely converted into energy, the amount of energy produced
E = mc2, m = 1 u = 1.6605 x 10-27 kg,c = 2.998 x 108 ms-1 = 1.6605 x 10-27 x (2.998 x 108)2J =14.920008 X 10-11 J
≈ 931 MeV (1 eV= 1.6602 x 10-19 J, 1 MeV = 106 eV)
7. Nuclear Fission is the process of splitting of a heavy nucleus into two lighter nuclei of almost equal masses with the liberation of energy.
Example: When \({ }_{92}^{235}U\) nuclei bombarded with slow neutrons, exploded into two fragments 56Ba and 36Kr.
{ }_{92}^{235} U+{ }_0^1 \mathrm{n} \rightarrow{ }_{92}^{236} \mathrm{U}^\rightarrow{ }_{56}{ }^{141} \mathrm{Ba}+{ }_{36}^{92} \mathrm{Kr}+{ }_{30}^1 \mathrm{n} \\ +\text { energy } \end{array}\)
The energy released in \({ }_{92}^{235}U\) fission is about 200 MeV. A nuclear reaction sustained by the product of the initial reaction leading from one reaction to the other consecutively, is called chain reaction.
Wbbse Class 10 Physical Science Chapter 7 Question And Answers
When one neutron is bombarded on \({ }_{92}^{235}U\) target then 3 neutrons are released. They are j slowed down to thermal neutron. Now they are used for further fission of \(3_{92}^{235}U\) nuclei releasing 9 new neutrons and so on.
8. A nuclear reactor is a device in which nuclear fission can be carried out through a sustained and controlled chain reaction. Main component of a nuclear reactor: Uranium isotopes (U235), Thorium isotope (Th232) etc are most commonly used fuels in the reactor.
10. Moderator is used to slow down the fast moving neutrons. Most commonly used moderators are graphite and heavy water (D2O).
11. Control material is used to control the chain reaction and to maintain a stable rate of reaction. Cadmium rods are used as control material. (Steel rod with a coating of boron is also used as a control rod)
12. Most commonly used coolants are water, N2,CO2.
13. Uses of nuclear reactor are:
(1)In electric power genertaion
(2) To produce radioisotopes etc.
14. Nuclear Fusion is a process in which two light nuclei are fused or combined at a very high temperature to form a heavy nucleus. This process releases a large amount of energy. High pressure (≈ 106 atm) and high temperature (≈ 107 K to 108K are required for fusion. So the fusion reaction is called a thermonuclear reaction.
Examples:
1. \(
{ }_1^2 \mathrm{H}+{ }_1^2 \mathrm{H} \stackrel{\text { Fusion }}{\longrightarrow}{ }_2^3 \mathrm{He}+{ }_1^0 \mathrm{n}+\text { energy }
(3.7 MeV)\)
Two \({ }_1^2 \mathrm{H}\) nuclei are fused to produce a \({ }_2^3 \mathrm{He}\) nucleus, a neutron, and energy (3.7 MeV approx).
2. In the Sun and some stars the source of energy is the fusion of protons to form a helium nucleus, positrons, and energy.
\(\begin{array}{r}{ }_1^2 \mathrm{H}+{ }_1^2 \mathrm{H}+{ }_1^2 \mathrm{H}+{ }_1^2 \mathrm{H} \stackrel{\text { Fusion }}{\longrightarrow}{ }_2^4 \mathrm{He}+2{ }_1^{\mathrm{O}} \mathrm{e} \\
+\text { energy (26 MeV) }
\end{array}\)
Chapter 7 Atomic Nucleus Topic B Nuclear Energy Short And Long Answer Type Questions:
Question 1. What is nuclear reaction? Write down Einstein’s principle of equivalence of mass and energy.
Answer:
Nuclear reaction:
1. Nuclear reaction is a process in which two nuclei, or else a nucleus of an atom and a subatomic particle from outside the atom, collide to produce one or more nuclides that are different from the initial nuclide(s).
2. According to Einstein’s theory of relativity, mass is concentrated energy. It is possible to convert mass into energy and energy into mass. If an amount of mass m of a substance is converted fully into energy, then an amount of energy E=mc2 is released where c = 2.998 x 108m/s = speed of light in vacuum.
Question 2. What is mass defect? Calculate the mass defect of the nucleus with mass M .Given, the mass of a proton = mp and the mass of a neutron = mn.
Answer:
Mass defect:
1. The mass of a nucleus is slightly less than the mass of the sum of protons and neutrons present in the nucleus. This difference between the two masses is called the mass defect.
2. According to the above question, the atomic number and the mass number of the atom are Z and A, respectively. If the masses of the proton respectively and the mass of the nucleus of the atom is M, then the total mass of the nucleons = Z • mp + (A – Z)mn.
∴ mass defect = Z • mp + (A – Z)mn – M
Question 3. What is binding energy? Calculate the binding energy of the nucleus with mass M. Given the mass of a proton = mp and the mass of a neutron = mn.
Answer:
Binding energy:
1. Binding energy is defined as the minimum energy required to disassemble a nucleus of an atom into its constituent particles. It is the equivalent amount of energy of mass defect.
2. According to the above question, the atomic number and the mass number of the atom are Z and A, respectively. If the masses of the proton and the neutron are mp and mn, respectively and the mass of the nucleus of the atom is M, then total mass of the nucleons = Z • mp + (A-Z)mn
∴ mass defect = Z • mp + (A – Z)mn– M and hence binding energy = {Z-mp + (A-Z)mn-M}c2
∴ where c is the speed of light in vacuum.
Wbbse Class 10 Physical Science Chapter 7 Question And Answers
Question 4. Calculate the equivalent amount of energy when 1 u of mass is converted fully into energy. Calculate the binding energy of a 4He2 nucleus. Given, mn = 1.007276 u,mn = 1.008665, mass of 4He2 nucleus = 4.001505u.
Answer:
1. Here, m = 1u = 1.66 x 10-27 kg
According to the equation E=mc2, the equivalent amount of energy = 1.66 x 10-27 x (2.998 x 108)2 = 14.92008 x 10-13nJ
Again, 1 MeV = 1.6022 x 10-13 J
\(E=\frac{14.92008}{1.6022} \times \frac{10^{-11}}{10^{-13}} \mathrm{MeV}\)= 931.2 MeV or, 1 u =931.2 MeV.
2. Mass defect of 4He2 nucleus = (2mp+2 mn)-M = (2 X 1.007276 + 2 X 1.008665) – 4.001505 = 0.0304 u (approx.)
∴ binding energy of 4He2 nucleus = 0.0304 x 931.2 MeV = 28.3 MeV (nearly)
Question 5. What do you mean by a chain reaction? What is a nuclear reactor?
Answer:
Chain reaction:
1. In nuclear fission due to the bombardment of neutrons on each 235U atom, high speed neutrons are ejected from the reaction. These are called secondary neutrons. These secondary neutrons interact with the surrounding uranium nucleus.
If sufficient fissile fuel is present, some of these neutrons may be absorbed and cause more fissions. Thus, the cycle repeats and the process of nuclear fission continues spontaneously. This type of spontaneous reaction is called a chain reaction.
2. A nuclear reactor is an arrangement used to initiate and control a sustained nuclear chain reaction. Nuclear reactors are used at nuclear power plants mainly for electricity generation.
Question 6. What is nuclear fission?
\(
{ }_{92}^{235} \mathrm{U}+{ }_0^1 \mathrm{n} \longrightarrow{ }_{54}^{134} \mathrm{xe}+{ }_{38}^{100} \mathrm{Sr}+{ }_2^1 \mathrm{n}
[235.0439u] [1.0087u] [133.9054u] [99.9354u] +
energy \)
Wbbse Class 10 Physical Science Chapter 7 Question And Answers
How much mass is reduced in the given nuclear fission?
Answer: Breaking up of a heavy nucleus into two nuclei of almost equal masses is called nuclear fission.
In the given equation, initial mass before reaction,
m1 = mass of U-235 nucleus + mass of a neutron = 235.0439 + 1.0087 = 236.0526 u
Final mass after reaction, m2 = mass of (Xe-134 + Sr-100 + 2 neutrons)= 133.9054 + 99.9354 + 2 x 1.0087 = 235.8583U
∴ reduction of mass, m = m1 -m2 = 236.0526 – 235.8583 = 0.1944 u
Question 7. Write down the names of some non conventional sources of energy other than atomic energy. What are the advantages in the production of atomic energy?
Answer: Some sources of non-conventional energy other than atomic energy are solar energy, wind energy tidal energy etc. Production of atomic energy is not affected by any natural event like cyclones, storms, rain, earthquakes etc. Atomic energy can be produced day and night over all the year. But this advantage is not there in the case of the production of other energies. This is the advantage of the production of atomic energy.
Question 8. What are the advantages of atomic energy as a fuel compared to fossil fuel?
Answer:
Advantages of atomic energy over energy from fossil fuel:
| Energy from fossil fuel | Atomic Energy |
| 1. Due to the rampant use of fossil fuels (like coal, petrol, diesel, kerosene etc.), amount. of carbon dioxide and other Greenhouse gases is increasing in the atmosphere. | 1. Production of harmful gases reduce owing to the use of atomic energy. |
| 2. The amount of fossil fuel used to get a certain amount of energy is slowly pushing us towards a serious fuel crisis. This is a major problem at present for human civilisation. | 2. A huge amount of energy is available due to nuclear fission from a very small amount of material. This is not possible from any other source and also is a great savior compared to any other fuel. For example, nearly 3000 tons of coal have to be burnt to get the same amount of energy (nearly 7.4 x 1010J) that is available from fission of only 1 g of U-235. |
Question 9. Why is a fission reaction carried out before a fusion reaction? Several lacs of people were killed in Japan in 1945 due to the explosion of an atomic bomb. In 1986, the nuclear reactor at Chornobyl of Ukraine went out of control and the residents of that town suffered nearly the same fate. Is.there any difference in the scientific causes of these two incidents?
Answer:
1. 107°C to 108°C temperature is required for fusion of the nuclei. This high temperature cannot be produced in a simple way This high temperature can be produced by the process of takes place before a fusion reaction.
2. The first incident was due to the bad intention of a class of warmongers. Due to uncontrolled nuclear fission, huge amount of heat energy is produced in this type of atomic explosion. Radioactive radiation is also emitted in it. Due to these two reasons, a lot of people were killed.
The second one was simply an undesirable accident. In a nuclear reactor, heat energy is converted into electrical energy by causing controlled nuclear fission. In other words, atomic energy is utilised in a peaceful way through this process for the welfare of mankind.
But unfortunately, on 26th April 1986, the process of nuclear fission in a nuclear reactor at Chornobyl of Ukraine went out of control and emitted a huge amounts of radioactive rays. As a result, the residents of the city became the victims of radioactivity for a long time.
Question 10. What are used as:
1. Fuel,
2. Moderator,
3. Control rods and
4. Coolant in a nuclear reactor and what are their functions?
Answer:
| Name of the part | Main material used | Function |
| 1. Fuel | Uranium (a radioactive element) [U-235] | U-235 is bombarded with thermal neutrons bringing about fission. |
| 2. Moderator | Heavy water (D2O ) or graphite | Neutrons with high kinetic energy generated due to nuclear reactions are slowed down by it |
| 3. Control rods | Cadmium (Cd), hafnium (Hf), or boron (B) coated steel rods | To absorb excess thermal neutrons that are not required. |
| 4. Coolant | Generally water | To absorb heat energy that is produced in the core due to nuclear reactions |
Question 11. Explain nuclear fusion with an example. Explain the main source of energy for sun and other stars.
Answer:
1. An example of nuclear fusion is given below.
Here, two deuterium nuclei combine together to form one helium ( 3He2) nucleus and one neutron. The sum of the masses of helium ( 3He2) and neutron is slightly less than the sum of the masses of two deuteriums. This reduced mass is converted into energy.
2. The main process of producing energy for any star like sun is nuclear fusion. The main fuel of a star is hydrogen. The process of fusion in a star is brought about through some cycles. Generally, it is said that in each cycle, four hydrogen (1H1) nuclei join to produce one helium (4He2) and two positrons (0e1).
Physical Science Class 10 West Bengal Board
\(4_1^1 \mathrm{H} \longrightarrow{ }_2^4 \mathrm{He}+2_1^0 \mathrm{e}\)The sum of the masses of one helium (4He2 ) and two positrons (0e1) is less than the combined mass of four hydrogen nuclei. This decrease in mass is transformed into energy. In sun 12 crore tons of hydrogen is converted into helium in every minute and a huge amount of heat energy is thus produced. The sun has been radiating heat energy in this way for the last 460 crore years.
Question 12. What is nuclear fusion?
\(\begin{aligned}
& { }_1^2 \mathrm{H}+{ }_1^2 \mathrm{H} \longrightarrow{ }_2^3 \mathrm{He}+{ }_0^1 \mathrm{n} \text { +energy } \\
& {[2.015 \mathrm{u}]} \\
&
\end{aligned}\)
Calculate the amount of energy released in this process by talking 1u = 931.2 MeV.
Answer:
1. Nuclear fusion is a process in which two light nuclei are fused or combined at a very high temperature to form a heavy nucleus. This process releases a large amount of energy.
2. Mass of 2 deuterons in the given equation before reaction, m1 = 2 x 2.015 = 4.030 u.
Final mass after reaction, m2 =\({ }_2^3 \mathrm{He}+{ }_0^1 n\) = 3.017 + 1.009 = 4.026 u decrease in mass, m = m1 – m2 = 4.030-4.026 = 0.004 u
amount of energy released = 0.004 u equivalent amount of energy = 931.2 x 0.004 = 3.725 MeV (approx.)
Question 13. Write down the diffreneces between nuclear fission and nuclear fussion.
Answer:
The differences between nuclear fission and nuclear fusion are:
| Nuclear fission | Nuclear fusion |
| 1. A heavy nucleus is split into two nuclei of almost equal masses in this process. | 1. A few light nuclei are fused together to form a heavy nucleus in this process. |
| 2. The energy produced in this process is less than the energy produced by the fusion of materials of equal masses. | 2. The energy produced in this process is more than the energy produced by fission of equal masses. |
| 3. Thermal neutrons are required in this process to bombard the target nucleus. | 3. No bombarding particle is required in this process. |
| 4. This process takes place at normal -temperature. | 4. This process takes place at a temperature between 107oC and 108oC. |
| 5. Radioactive rays are emitted in this process. | 5. No radioactive rays are emitted in this process. |
Chapter 7 Atomic Nucleus Topic B Nuclear Energy Very Short Answer Type Questions Choose The Correct Answer:
Question 1. The main cause of solar energy is
1. Nuclear fission and fusion
2. Nuclear fission
3. Nuclear fusion
4. Chemical reaction
Answer: 3. Nuclear fusion
Question 2. \({ }_{92}^{235} U+{ }_0^1 n \longrightarrow{ }_{56}^{141} B a+{ }_{36}^{92} \mathrm{Kr}+{ }_0^1 n\)
1. 1
2. 2
3. 3
4. 4
Answer: 3. 3
Question 3. What is the average binding energy of each nucleon inside a nucleus to make the nucleus stable?
1. Nearly 2 MeV
2. Nearly 2.5 MeV
3. Nearly 3 MeV
4. Nearly 8 MeV
Answer: 4. Nearly 8 MeV
Question 4. 1 eV = how many J?
1. 3.2 x 10-19
2. 1.6 x 10-19
3. 4.8 X 10-19
4. 6 4 X 10-19
Answer: 2. 1.6 x 10-19
Question 5. 1 MeV = how many J?
1. 1.6 x10-13
2. 3.2 x 10-13
3. 4.8 x 10-13
4. 6.4 x 10-13
Answer: 1. 1.6 x10-13
Question 6. Binding energy per nucleon is maximum in
1.60Ni
2. 56Fe
3. 58Fe
4. 62Ni
Answer: 4. 62Ni
Question 7. Value of binding energy per nucleon of 62Ni is approximately
1. 8.0 MeV
2. 9.2 MeV
3. 8.8 MeV
4. 8.2 MeV
Answer: 3. 8.8 MeV
Question 8. How many times more energy is released during fusion of 1 g of hydrogen than during fission of lg of uranium ( 235U92)?
1. 2.3
2. 4.3
3. 7.3
4. 10.3
Answer: 3. 7.3
Question 9. How much energy is produced if 0.1 u amount of mass is converted into energy?
1. 186.3 MeV
2. 46.575 MeV
3. 93.12 MeV
4. 372.6 MeV
Answer: 3. 93.12 MeV
Question 10. Size of the nucleus is of the order of
1. 10-10 m
2. 10-15 m
3. 10-12 m
4. 10-19 m
Answer: 2. 10-15 m
Question 11. Nuclear binding energy is equivalent to
1. Mass of proton
2. Mass of neutron
3. Mass of nucleus
4. Mass defect of nucleus
Answer: 4. Mass defect of nucleus
Question 12. The energy equivalent to 1 kg of matter is about
1. 10-15 J
2. 10 J
3. 10-10 J
4. 1017 J
Answer: 4. 1017 J
Question 13. Average binding energy per nucleon in the nucleus of an atom is approximately
1. 8eV
2. 8 keV
3. 8 MeV
4. 8J m
Answer: 3. 8 MeV
Question 14. A moderator is used in nuclear reactor in order to
1. Slow down the speed of the neutrons
2. Accelerate the neutrons
3. Increase the number of neutrons
4. Decrease the number of neutrons
Answer: 1. Slow down the speed of the neutrons
Question 15. The control rod in a nuclear reactor is made of
1. Uranium
2. Cadmium
3. Plutonium
4. Graphite
Answer: 2. Cadmium
Question 16. The process by which a heavy nucleus splits into light nuclei is known as
1. Fission
2. Fusion
3. Chain reaction
4. Meltdown
Answer: 1. Fission
Question 17. During the nuclear fusion reaction
1. A heavy nucleus breaks into two fragments by itself
2. A light nucleus bombarded by thermal neutrons breaks up
3. A heavy nucleus bombarded by thermal neutrons breaks up
4. Two light nuclei combine to give a heavier nucleus and possible other products
Answer: 4. Two light nuclei combine to give a heavier nucleus and possible other products
Question 18. Fusion reaction takes place at high temperature because
1. Atoms are ionised at high temperature
2. Molecules break up at high temperature
3. Nuclei break up at high temperature
4. Kinetic energy is high enough to overcome repulsion between nuclei
Answer: 4. Kinetic energy is high enough to overcome repulsion between nuclei
Question 19. The explosion of the atomic bomb takes place due to
1. Nuclear fission
2. Nuclear fusion
3. Melting
4. Evaporation
Answer: 1. Nuclear fission
Question 20. The mass equivalent of 931 MeV energy is
1. 1.66 x 10-27 kg
2. 6.02 x 10-24 kg
3. 1.66 x 10-20 kg
4. 9.11 x 10-31 kg
Answer: 1. 1.66 x 10-27 kg
Question 21. A chain reaction continues due to
1. Large mass defect
2. Large energy
3. Production of more neutrons in fission
4. High temperature
Answer: 3. Production of more neutrons in fission
Question 22. Heavy water ( D2O) is used as moderator in a nuclear reactor. The function of the moderator is
1. To control the energy released in the reactor
2. To absorb neutrons and stop chain reaction
3. To cool the reactor fast
4. To slow down the speed of neutrons
Answer: 4. To slow down the speed of neutrons
Chapter 7 Atomic Nucleus Topic B Nuclear Energy Answer In Brief:
Question 1. What is the temperature required to bring about nuclear fusion?
Answer: Nuclear fusion takes place at a temperature of 107oC to 108oC.
Question 2. What is the main source of energy for the sun and the stars?
Answer: Nuclear fusion is the main source of energy for the sun and the stars
Question 3. Name one radioactive material which is much used as fuel in a nuclear reactor.
Answer: Uranium, a radioactive material, is generally used as fuel in a nuclear reactor.
Question 4. What is the role of heavy waters in a nuclear reactor?
Answer: Heavy water is used in a nuclear reactor to slow down the speed of neutrons.
Question 5. The binding energy of the 4He2 nucleus is 28.2 MeV. What do you understand by this statement?
Answer: The given statement means that a minimum energy of 28.2 MeV is required to separate 2 protons and 2 neutrons from a helium nucleus to make them free.
Question 6. Which element has the highest binding energy per nucleon?
Answer: 62Ni has the highest binding energy per nucleon.
Question 7. What do you understand by mass defect?
Answer: The mass of a nucleus is slightly less than the mass of the sum of protons and neutrons present in the nucleus, this difference of two masses is called the mass defect.
Question 8. What is binding energy of a nucleus?
Answer: Nuclear binding energy is the minimum energy that is required to disassemble the nucleus of an atom into its component parts, i.e., neutrons and protons.
Question 9. Who did invent the formula of equivalence of mass and energy?
Answer: Albert Einstein invented the formula.
Question 10. Write down Einstein’s formula for mass-energy equivalence.
Answer: Formula: E=mc2, where m = mass of material, c – speed of light in vacuum, and E is the amount of energy equivalent to mass m.
Question 11. What is nuclear fission?
Answer: Nuclear fission is the process of splitting of a heavy nucleus into two lighter nuclei of comparable masses with the liberation of energy.
Question 12. What is the main source of energy gained in nuclear fusion or fission?
Answer: The main source of energy gained in nuclear fusion or fission is a decrease or reduction in mass.
Question 13. Which nuclear process was followed to manufacture an atomic bomb?
Answer: Nuclear fission was followed to manufacture an atom bomb.
Question 14. Which particle is used as a bombarding particle to bombard the target nucleus in the process of nuclear fission?
Answer: Neutron is used as a bombarding particle.
Question 15. How much energy is produced if 1 u amount of mass is converted into energy?
Answer: 931.2 MeV (approx.) energy is produced if lu amount of mass is converted into energy.
Question 16. What is a thermal neutron?
Answer: A neutron with a high kinetic energy of about 10-2 eV is called thermal neutron.
Physical Science Class 10 West Bengal Board
Question 17. Write down an use of thermal neutron.
Answer: Thermal neutron is used to split a heavy nucleus into two or more lighter nuclei in nuclear fission.
Question 18. Is the Particle produced in nuclear fusion radioactive or non-radioactive?
Answer: The particle produced in nuclear fusion is non-radioactive.
Question 19. Which process is carried out in a nuclear reactor?
Answer: The process of nuclear fission is carried out in a controlled way in a nuclear reactor.
Question 20. Can nuclear fission process be controlled?
Answer: Yes, the process of nuclear fission can be controlled.
Question 21. Complete the following reaction: \({ }_{88}^{226} R a \longrightarrow ?+{ }_{86}^{222} R n\)
Answer: \({ }_{88}^{226} \mathrm{Ra} \rightarrow{ }_2^4 \mathrm{He}+{ }_{86}^{222} \mathrm{Rn}\)
Question 22. Complete the following reaction: \({ }_6^{14} C \longrightarrow ?+{ }_7^{14} N\)
Answer: \({ }_6^{14} \mathrm{C} \rightarrow{ }_{-1}^0 \mathrm{e}+{ }_7^{14} N\)
Question 23. Complete the following reaction: \({ }_{90}^{234} \mathrm{Th} \longrightarrow{ }_{91}^{234} \mathrm{~Pa}+?\)
Answer: \({ }_{90}^{234} \mathrm{Th} \rightarrow{ }_{91}^{234} \mathrm{~Pa}+{ }_{-1}^0 \mathrm{e}\)
Question 24. Complete the following reaction: \({ }_{92}^{238} \mathrm{U} \longrightarrow ?+{ }_2^4 \mathrm{He}\)
Answer: \({ }_{92}^{238} \mathrm{U} \rightarrow{ }_{90}^{234} \mathrm{Th}+{ }_2^4 \mathrm{He}\)
Question 25. What is the amount of nuclear binding energy corresponds to mass defect Am?
Answer: Nuclear binding energy corresponds to mass defect Δm is = Δm . c2, c = speed of light in vacuum.
Question 26. The expected mass of a helium nucleus is 4.0320 u and its actual mass is 4.0015 u. Find its mass defect.
Answer: Mass defect of a helium nucleus is Δm = 4.0320 – 4.0015 = 0.0305 u.
Question 27. What is the relation between mass defect and nuclear binding energy?
Answer: Nuclear binding energy is energy equivalent to the mass defect of a nucleus.
Question 28. Is the law of conservation of mass applicable in case of nuclear reaction?
Answer: In case of nuclear reaction the law of conservation of mass is not applicable.
Physical Science Class 10 West Bengal Board
Question 29. Is the law of conservation of mass number and the law of conservation of atomic number applicable in case of nuclear reaction?
Answer: Yes, the law of conservation of mass number and the law of conservation of atomic number are applicable in case of nuclear reaction.
Question 30. What is a nuclear reactor?
Answer: A nuclear reactor is an arrangement used to initiate and control a sustained nuclear chain reaction.
Question 31. What is the role of moderators in a nuclear reactor?
Answer: Moderator is used to slowing down the speed of neutrons.
Question 32. What is the role of the control rod in a nuclear reactor?
Answer: The control rod absorbs surplus thermal neutrons.
Question 33. What material is generally used as a control rod in a nuclear reactor?
Answer: Cadmium rod or steel rod with a coating of boron is generally used as a control rod.
Chapter 7 Atomic Nucleus Topic B Nuclear Energy Fill In The Blanks:
Question 1. The mass of a nucleus is slight ______ than the sum of the masses of neutrons and protons present in that nucleus.
Answer: Less
Question 2. The process of nuclear ______ is carried out before nuclear fusion takes place.
Answer: Fission
Question 3. Mass of the nucleus of deuterium (2H1) is ______ than the sum of masses of one proton and one neutron.
Answer: Less
Question 4. The chain reaction is observed in nuclear fission.
Answer:
Physical Science Class 10 West Bengal Board
Question 5. The main cause in producing energy for the sun is nuclear ________.
Answer: Fusion
Question 6. The fusion process occurs at a very high temperature. Such a process is called a _______ reaction.
Answer: Thermonuclear
Question 7. ________ is used as a projectile particle in a nuclear fission reaction.
Answer: Thermal/Slow
Question 8. Heavy water (D2O) is used as a _______ in nuclear reactors.
Answer: Moderator
Question 9. The greater is the binding energy the more ______ is the nucleus.
Answer: Stable
Chapter 7 Atomic Nucleus Topic B Nuclear Energy State Whether True Or False:
Question 1. High-energy neutrons are used in a nuclear reactor to initiate the fission reaction.
Answer: False
Question 2. Cadmium rods are used as moderators in a nuclear reactor.
Answer: False
Physical Science Class 10 West Bengal Board
Question 3. The higher the mass defect the higher is the stability of the nucleus.
Answer: False
Question 4. \({ }_0^1 \mathrm{n}+{ }_7^{14} \mathrm{~N} \longrightarrow{ }_1^0 \mathrm{H}+{ }_6^{15} \mathrm{C}\)
Answer: False
Question 5. The conversion of lu of mass results in 931.2 x 106 eV of energy.
Answer: True
Question 6. In sun and other stars, the energy is produced by nuclear fusion.
Answer: True
Question 7. Mass defect is always positive.
Answer: True
Question 8. Electron is used as an ideal particle for bombarding.
Answer: False
Question 9. Hydrogen bomb is made on the basis of nuclear fission reaction.
Answer: False
Question 10. The Fukushima nuclear plant disaster was a nuclear accident caused by a natural disaster tsunami.
Answer: True
Chapter 7 Atomic Nucleus Miscellaneous Type Questions Match The Columns:
Question 1.
| Column A | Column B |
| α-particle | 1. Electromagnetic radiation |
| β-particle | 2. 1H2 |
| γ-ray | 3. He2+ |
| Deuteron | 4. e- |
Answer:
α-particle: 3. He2+
β-particle: 4. e-
γ-ray: 1. Electromagnetic radiation
Deuteron: 2. 1H2
Question 2.
| Column A | Column B |
| α-decay | 1. Unchanged nucleus |
| β -decay | 2. Decrease in mass number |
| γ-decay | 3. Increase in atomic number |
Answer:
α-decay: 2. Decrease in mass number
β -decay: 3. Increase in atomic number
γ-decay: 1. Unchanged nucleus
Question 3.
| Column A | Column B |
| 1 u | 1. 6.642 X 10-24 g |
| Mass of α-particle | 2. E = mc2 |
| Equivalence of mass and energy | 3. 1H2 + 1H2 →2He3 + 0n1 |
| Nuclear fusion | 4. 931.2 MeV |
Answer:
1 u: 4. 931.2 MeV
Mass of α-particle: 1. 6.642 X 10-24 g
Equivalence of mass and energy: 2. E = mc2
Nuclear fusion: 3. 1H2 + 1H2 →2He3 + 0n1
WBBSE Solutions for Class 10 Physical Science and Environment
- Chapter 1 Environmental Concern
- Chapter 2 Behaviour of Gases
- Chapter 3 Chemical Calculations
- Chapter 4 Phenomena of Heat
- Chapter 5 Light
- Chapter 6 Current Electricity
- Chapter 8 Physical and Chemical Properties of Elements