21.

STATEMENT – 1
When ultraviolet light is incident on a photocell, its stopping potential is V₀ and the maximum kinetic energy of the photoelectrons is Kmax. When the ultraviolet light is replaced by X–rays, both V0 and Kmax increase.

STATEMENT – 2
Photoelectrons are emitted with speeds ranging from zero to a maximum value because of the range of frequencies present in the incident light.

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

• Statement – 1 is True, Statement – 2 is True; Statement – 2 is a correct explanation for Statement – 1.

• Statement – 1 is True, Statement – 2 is True; Statement – 2 is not the correct explanation for Statement – 1.

• Statement – 1 is True, Statement – 2 is True; Statement – 2 is not the correct explanation for Statement – 1.

A nucleus of mass M + Δm is at rest and decays into two daughter nuclei of equal mass M/2 each. The speed of light is c.
The binding energy per nucleon for the parent nucleus is E₁ and that for the daughter nuclei is E₂. Then

• E₁ = 2E₂

• E₂ = 2E₁

• E₁ > E₂

• E₁ > E₂

A nucleus of mass M + Δm is at rest and decays into two daughter nuclei of equal mass M/2 each. Speed of light is c.

The speed of daughter nuclei is

A radioactive nucleus (initial mass number A and atomic number Z) emits 3 α–particles and 2 positions. The ratio of number of neutrons to that of protons in the final nucleus will be

The combination of gates shown below yields

• OR gate

• NOT gate

• XOR gate

• XOR gate

If a source of power 4kW produces 10²⁰ photons/second, the radiation belongs to a part of the spectrum called

• X -rays

• ultraviolet rays

• microwaves

• microwaves

The potential energy function for the force between two atoms in a diatomic molecule is approximately given by  where a and b are constants and x is the distance between the atoms. If the dissociation energy of the molecule is D = [U(x = ∞) – U_{at equilibrium}], D is

• b²/2a

• b²/12a

• b²/4a

• b²/4a

The speed of light in the medium is

•  maximum on the axis of the beam

• minimum on the axis of the beam

• the same everywhere in the beam

• the same everywhere in the beam

An initially parallel cylindrical beam travels in a medium of refractive index μ(I) = μ₀ +μ₂I , where μ₀ and μ₂ are positive constants and I is the intensity of the light beam. The intensity of the beam is decreasing with increasing radius. 

As the beam enters the medium, it will

• travel as a cylindrical beam

• diverge

• converge

• converge

An initially parallel cylindrical beam travels in a medium of refractive index μ(I) = μ0 +μ2I , where μ0 and μ2 are positive constants and I is the intensity of the light beam. The intensity of the beam is decreasing with increasing radius.
The initial shape of the wavefront of the beam is

• convex

• concave

• convex near the axis and concave near the periphery

• convex near the axis and concave near the periphery