Question

Radiation of frequency 1.5 times the threshold frequency is incident on a photosensitive material. If the frequency of incident radiations is halved , the number of photoelectrons ejected per second becomes

• A. Zero
• B. Half of its initial value
• C. One fourth the initial value
• D. Three fourth the initial value

Answer 1

The correct option is A Zero

Radiation of frequency 1.5 times the threshold frequency is incident on a photosensitive material.
${\nu }_1=1.5{\nu }_0$
The frequency of incident radiations is halved and the intensity is doubled.

So,${\nu }_2={\nu }_1/2=0.75{\nu }_0$.

So now the incident frequency is less than the threshold frequency so the photoemission shall stop altogether.

So, the answer is option (A).