Question

Photoelectrons are emitted by making green light incident on a metallic surface. Which of the following lights can start photoelectric emission?
A. Yellow
B. Orange
C. Blue
D. Red

Answer 1

In order to explain this question, we should be aware of the process of photoelectric effect and also we should know how the photoelectrons emit the electromagnetic radiation when it strikes the surface of metal.

Complete step by step answer:
According to the above question, when the green light is incident on the metallic surface, then the photoelectrons are emitted from the metallic surface which means the threshold frequency of green light holds good. Because the green light frequency matches with the threshold frequency. When both the frequencies match each other hence electrons are able to emit from the surface of the metal.
The threshold frequency is the minimum frequency of incident radiation below which the photoelectric emission does not take place.
It can be explained by taking the concept of how frequency of light depends on wavelength of light. The frequency of light which is inversely proportional to the wavelength of light.
Here, the wavelengths of red, yellow and range light are greater therefore their frequencies are lesser, hence no photoelectrons will eject when these lights are made to fall on a metal surface.

Similarly, the wavelength of blue light is lesser than green light, its frequency is greater than green light hence, and photoelectrons will emit from the surface.
Hence the correct option is C.

So, the correct answer is “Option C”.

Note:
Photoelectric effect is the phenomenon in which when light which has a certain frequency hits the surface of the metal electron releases from the surface of the metal surface.
The green light of wavelength is larger than yellow and red, hence green light emits electrons when it is incident on a metal surface because its frequency is greater.