121.

If alpha, beta and gamma rays carry same momentum, which has the longest wavelength?

• Alpha rays

• Beta rays

• Gamma rays

• None, all have same wavelength

Assertion:  The binding energy per nucleon, for nuclei with atomic mass number A > 100 decreases with A. 

Reason:  The nuclear forces are weak for heavier nuclei.

• If both assertion and reason are true and reason is the correct explanation of the assertion

• If both assertion and reason are true but reason is not the correct explanation of the assertion

• If assertion is true, but reason is false

• Both assertion and reason are false statements

Assertion:  Cobalt-60 is useful in cancer therapy. 

Reason:  Cobalt-60 is a source of y-radiations capable of killing cancerous cells.

• If both assertion and reason are true and reason is the correct explanation of the assertion

• If both assertion and reason are true but reason is not the correct explanation of the assertion

• If assertion is true, but reason is false

• Both assertion and reason are false statements

The magnetic moment ( μ) of a revolving  electron around the nucleus varies with principal quantum number n as

•  μ ∝ n

•  μ  ∝ 1/n

•  μ ∝  n²

• μ ∝ 1/n²

A radioactive material has a half-life of 10 days. What fraction of the material would remain after 30 days?

• 0.5

• 0.25

• 0.125

• 0.33

According to Hubble's law, the redshift (Z) of a receding galaxy and its distance r from earth are related as

• Z ∝ r 

• Z ∝ 1/r

• Z ∝ 1/r²

• Z ∝ r^3/2 

Assertion:  It is not possible to use  ³⁵Cl  as  the fuel for fusion energy.

Reason: The binding energy of  ³⁵Cl is too small.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false

Assertion: The number of electrons in a p-type silicon  semiconductor is less than the number of electrons in a pure silicon semiconductor at room temperature.

Reason: It is due to law of mass action.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false

A nucleus of mass number A, originally at rest, emits on  $\mathrm{\alpha }$-particle with speed v. The daughter nucleus recoil with speed a speed 

• $\frac{2\mathrm{v}}{\mathrm{A} + 4}$

• $\frac{4\mathrm{v}}{\mathrm{A} + 4}$

• $\frac{4\mathrm{v}}{\mathrm{A} - 4}$

• $\frac{2\mathrm{v}}{\mathrm{A} - 4}$

When an electron-positron pair annihilates, the energy released is about

• 0.8 × 10^-13 J

• 1.6 × 10^-13 J

• 3.2 × 10^-13 J

• 4.8 × 10^-13 J