Question

A light of frequency three times the threshold frequency is incident on a photosensitive material. Maximum kinetic energy of photoelectrons, if frequency of the incident light becomes half of its initial value, becomes

• A. Four times of its initial value
• B. Half of its initial value
• C. Two times of its initial value
• D. One fourth of its initial value

Answer 1

The correct option is D One fourth of its initial value

The kinetic energy of photoelectrons is given by,

$K=hv-\varphi$

As per the initial situation,

$K_1=h\left(3v_0\right)-h{v}_0=2h{v}_0$

When the frequency of the incident light becomes half,

$K_2=h\left(\frac{3}{2}{v}_0\right)-h{v}_0=\frac{1}{2}h{v}_0$

So, $\frac{K_2}{K_1}=\frac{\frac{1}{2}h{v}_0}{2h{v}_0}=\frac{1}{4}$