Question

The critical frequency for emitting photo electrons from a metal surface is 5 x 10¹⁴ sec . What should be the frequency of radiation to produce photo electrons having twice the kinetic energy of those produced by the radiation of frequency 10¹⁵ sec^-1.

Answer 1

Given critical frequency = 5 x 10¹⁴ sec^-1

When surface is exposed to frequency of 10¹⁵ sec^-1

Now for II case, if K.E. becomes twice of this, then

New K.E. = 2 x 5 x h x 10¹⁴