User:Kamal Krishna

Problem arising if we consider light as a wave 1)	Intensity Problem 2)	Frequency Problem 3)	Time Dilation Problem

Intensity problem

In wave theory of light, if we increase the intensity of beam of light, we are increasing the magnitude of oscillating electric field vector E. We know that the force that is exerted on electron by an electric field E is eE. So on increasing intensity we are increasing E and consequently we are increasing the exerted force on electrons. So, the energy associated with electron should be more.

But experiment shows that the energy of the electron does not depend upon the intensity of light.

This problem does not arise if we consider light as a photon having energy hv.

Where h is planks constant The frequency problem

According to wave theory of light the photoelectric effect can occur at any frequency of the incident of light, provided that the light is intense enough.

But the experiment shows that there is cutoff frequency below which there is no photoelectric effect. No matter how intense is the light is.

Time dilation problem

According to wave theory, the energy of the ejected photoelectron must be soaked up from the incident wave. The effective area from which the electron soaked up this energy can not be greater than the cross section of an atom. Thus if the light is feeble enough there should be measurable time delay between when the electron has accumulated sufficient energy to emerge from it. But there is no such time delay has been observed.