Two monochromatic beam A and B of equal intensity I, hit a screen. The number of photons hitting the screen by beam A is twice that by beam B. Then what inference can you make about their frequencies?

Explanation

Given , intensity of beams A and B, `I_A=I_B=I and n_A = 2n_B` where `n_A and n_B` are the number of photons falling per second of beams A and B respectively.
Let energy of incident photon of beam `A = hv_A`
and energy of incident photon of beam `B = hv_B`
As `I=n_ahv_A=n_bhv_B`
`impliesn_ahv_A =n_bhv_B`
`implies(v_A)/(v_B)=(n_B)/(n_A)=(n_B)/(2n_B)=1/2`
`impliesv_B=2v_A`
Thus, frequency of beam B is twice that of beam A .