Question

Light of frequency $1.5$ times the threshold frequency is incident on a photosensitive material photoelectric current is emitted. If the frequency of light is halved and intensity is doubled, the photoelectric current becomes:

• A. 4 times the original current
• B. 2 times the original current
• C. half the original current
• D. zero times the original current

Answer 1

Answer: (D)

The minimum frequency of light which can emit photoelectrons from a material is called the threshold frequency of that material. If the frequency of incident light is less than threshold frequency $(v_0)$ no photoelectrons are emitted whatever be the intensity of light. When frequency of incident light is halved, its frequency becomes $\frac{v_0}{2}$ which is less than threshold frequency $v_0$ . Hence, no photo- electric emission will take place.