NCERT Solutions for Class 12 Help.html Physics Part Ii Chapter 13 Nuclei

Name the electromagnetic radiations used for (a) water purification, and (b) eye surgery

Explain the processes of nuclear fission and nuclear fusion by using the plot of binding energy per nucleon (BE/A) versus the mass number A.

A radioactive isotope has a half-life of 10 years. How long will it take for the activity to reduce to 3.125 %?

The above is a plot of binding energy per nucleon Eb, against the nuclear mass M; A, B, C, D, E, F correspond to different nuclei. Consider four reactions:

(i) A + B → C + ε  (ii) C → A + B + ε
(iii) D + E → F + ε and (iv) F → D + E +ε

where ε is the energy released? In which reaction is ε positive?

• (i) and (iv)

• (i) and (iii)

• (ii) and (iv)

• (ii) and (iii)

The transition from the state n = 4 to n = 3 in a hydrogen-like atom results in ultraviolet radiation. Infrared radiation will be obtained in the transition from

• 2 → 1

• 3 → 2

• 4 → 2

• 5→ 4

This question contains Statement -1 and Statement-2. Of the four choices given after the statements,
Choose the one that best describes the two statements.
Statement – I: Energy is released when heavy nuclei undergo fission or light nuclei undergo fusion.
and
Statement – II: For heavy nuclei, binding energy per nucleon increases with increasing Z while for light nuclei it decreases with increasing Z.

• Statement – 1is false, Statement – 2 is true.

• Statement – 1is true, Statement – 2 is true; Statement -2 is correct explanation for Statement-1.

• Statement – 1is true, Statement – 2 is true; Statement -2 is not a correct explanation for Statement-1.

• Statement – 1 is true, Statement – 2 is False.

If M₀ is the mass of an oxygen isotope ₈O¹⁷ , Mp and M_N are the masses of a proton and a neutron respectively, the nuclear binding energy of the isotope is

• (M₀ – ⁸M_P) C²

• (M₀ – ⁸M_P – ⁹M_N) C²

• M₀C²

• (M₀ – ¹⁷ M_N) C₂

In gamma-ray emission from a nucleus

• both the neutron number and the proton number change

• there is no change in the proton number and the neutron number

• only the neutron number changes

• only the proton number changes

The half-life period of a radio-active element X is same as the mean life-time of another radio-active element Y. Initially, they have the same number of atoms. Then

• X will decay faster than Y

• Y will decay faster than X

• X and Y have same decay rate initially

• X and Y decay at same rate always

When ₃Li⁷ nuclei are bombarded by protons, and the resultant nuclei are ₄Be⁸ , the emitted particles will be

• neutrons

• alpha particles

• beta particles

• gamma photons