Question

For photoelectric effect, the incident light must be in the region of: a) red b) yellow c) blue or ultraviolet d) entire visible region

Answer 1

For photoelectric effect, the incident light must be at a region where it can attain the threshold frequency.
Threshold frequency is most commonly found in ultraviolet region.
So c) blur or ultraviolet region is ur required answer.

Hope I helped u

Answer 2

Correct Answer is : C

Explanation :

Photo electric emission is possible by radiations of wavelength less than green light,
Because the wavelength violet less than the wavelength of green.λv<λg

hence the correct answer will be blue or ultraviolet