There are two black bodies A and B with temperatures 1500 k and 3600 k respectively .
Photons having wavelength equal to the wavelength corresponding to maximum spectral radiancy of A & B (say `lambda_A and lambda_B` respectively) are incident on a metal sphere of radius 12 cm having work-function 1.2 eV. The maximum kinetic energies of the electrons emitted by these photons are in the ratio 1:3 .
Find the wavelengths `lambda_A and lambda_B`.
if `10^(12)` photons of wavelength `lambda_B` are incident per second and photo electric efficiency is one electron per `10^6` photons , find the time after which emission of photo-electrons will stop. in this case assume that `lambda_A` is not present.

Explanation

`lambda_b=(12375)/(9.6)A=1289A,lambda_a=3093.75a,t=700 "sec"`