Answer the following.
Why energy of each produced ‘$\gamma$’ photon is 0.511 MeV?
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Nuclei - ISC Class 12 Physics Questions with Answers, Page 2
52 past-paper questions on Nuclei from ISC Class 12 Physics papers (2027-2018), newest first, in full. Questions 21-40 are on this page, 20 to a page. Tap "Show answer" under a question to see its answer.
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Answer the following.
(a)[2.5]
A group of students went on an educational tour of Bhabha Atomic Research Centre, Mumbai. They visited various nuclear reactors like Apsara, Cirus, Zerlina and Dhruv and observed that Apsara was a swimming pool type reactor. The teacher explained how water slows down fast moving neutrons and absorbs the heat produced in the reactor.
(1) What is the use of a nuclear reactor?
(2) What is the name given to a material which slows down fast moving neutrons?
(3) State how a nuclear reactor can be shut down in case of an emergency.
(b)[2.5]
(1) What is meant by the statement: ‘Angular momentum of an orbiting electron is quantised’?
(2) What is the physical significance of the fact that total energy of an orbiting electron is negative?
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Answer the following.
(a)[1.6666666666666667]
Write a balanced equation of a nuclear fission reaction taking place in a nuclear reactor.
(b)[1.6666666666666667]
By performing necessary calculations, determine which one of the following nuclei is more stable:
$^4\text{He}$ nucleus having binding energy of $28.8\text{ MeV}$ or $^9\text{Be}$ nucleus having binding energy of $63\text{ MeV}$.
(c)[1.6666666666666667]
(1) Draw energy level diagram of hydrogen atom showing at least four (lowest) energy levels.
(2) Show any one transition on this diagram which results in the emission of light energy.
Draw: energy level diagram of hydrogen atom
Must show: four lowest energy levels: n=1, 2, 3, 4 with corresponding energy values, one transition resulting in emission of light energy (visible light: Balmer series)
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Solve the following.
Calculate the ratio of the radii.
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Draw the following.
A graph showing the variation of binding energy per nucleon with mass number is given below. In the graph mark regions where nuclei are: (a) Prone to fusion, (b) Prone to fission. (c) Give a reason for your marking.
Draw: regions on binding energy per nucleon curve prone to fusion and fission
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Answer the following.
In a nuclear reactor, state the use of the following:
(a)[1.0]
Graphite rods
(b)[1.0]
Cadmium rods
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Answer the following.
(a)[1.6666666666666667]
Calculate mass defect and binding energy of ${}^{20}_{10}\text{Ne}$ nucleus, given:
Mass of ${}^{20}_{10}\text{Ne} = 19.992397\text{ u}$
Mass of ${}^1_1\text{H} = 1.007825\text{ u}$
Mass of ${}^1_0\text{n} = 1.008665\text{ u}$
(b)[1.6666666666666667]
State the Bohr’s postulate of angular momentum of an electron.
(c)[1.6666666666666667]
(1) What is the velocity of an electron in the $3^{\text{rd}}$ orbit of hydrogen atom if its velocity in the $1^{\text{st}}$ orbit is $v_0$?
(2) Radius of the $1^{\text{st}}$ orbit of hydrogen atom is $r_0$. What will be the radius of the $4^{\text{th}}$ orbit?
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Answer in one word.
Name the type of nuclear reaction that takes place in the core of the Sun.
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Answer the following.
State the function of a moderator in a nuclear reactor.
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Answer the following.
Name any two essential parts of a nuclear reactor. State the function of any one of them.
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Answer the following.
State any two differences between Nuclear fusion and Nuclear fission.
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Answer the following.
What is the essential difference between the working of a fission bomb and a nuclear reactor?
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Answer the following.
Mr. Ravi had been living in a small town with his family for many years. He decided to shift to a city when he learnt that a nuclear power plant would be built in his town. His son Prakash, who was a science teacher, did not agree with his father’s decision. Prakash explained to his father how mass defect during nuclear fission released energy. He assured his father that the authorities were taking all the possible safety measures to avoid any kind of nuclear mishap. Mr. Ravi understood the scientific explanation given by his son and decided not to shift to another place.
(i)[1.0]
What is the cause of energy generation of a nuclear reactor during nuclear fission?
(ii)[1.0]
Write one nuclear reaction for nuclear fission that takes place in a nuclear reactor.
(iii)[1.0]
Give the formula for the energy generation that takes place in the nuclear reactor.
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Solve the following.
Calculate the minimum amount of energy which a gamma ray photon should have for the production of an electron and a positron pair.
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Answer the following.
Half life ($T$) and disintegration constant ($\lambda$).
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Solve the following.
Calculate binding energy of oxygen nucleus ($^{16}_{8}\text{O}$) from the data given below:
Mass of a proton = $1\cdot007825\text{ u}$
Mass of a neutron = $1\cdot008665\text{ u}$
Mass of ($^{16}_{8}\text{O}$) = $15\cdot994915\text{ u}$
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Choose the correct option.
In a nuclear reactor, cadmium rods are used as:
- (a)Control rods
- (b)Fuel rods
- (c)Coolant
- (d)Moderator
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Answer the following.
Mean life ($\tau$) and disintegration constant ($\lambda$).
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Choose the correct option.
In a gamma ray emission from nucleus:
- (a)only the number of protons change.
- (b)the number of protons and neutrons, both change.
- (c)there is no change in the number of protons and the number of neutrons.
- (d)only the number of neutrons change.
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Solve the following.
Copy and complete the following table for a radioactive element whose half-life is 10 minutes. Assume that you have 30g of this element at $t = 0$.
| $t$ (minute) | 0 | 20 | 30 |
|---|---|---|---|
| Amount of radioactive element left in gm | 30 | -- | -- |
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