question_answer

In a photo electric experiment, it was found that the stopping potential decreases from 1.85 V  to  0.82 V as the wavelength of the incident light is varies from 300 nm to 400 nm. The value of the Planck constant from these data is:

A)           

B)  

C)           

D)  

Correct Answer: A

Solution :

The maximum kinetic energy of a photoelectron is and the stopping the potential is             If are the stopping potential at wavelength  and  respectively.             and     This gives,