Ultraviolet light of wavelength `2271 Å` from a 100 W mercury source irradiates a photo-cell made of molybdenum metal. If the stopping potential is `-1.3 V`, estimate the work function of the metal. How would the photo-cell respond to a high intensity `(~10^(5) W m^(2))` red light of wavelength `6328 Å` produced by a He-Ne laser ?

Explanation

`phi_(0)=hv-eV_(0)=6.7xx10^(-19)J=4.2eV,v_(0)=(phi_(0))/(h)=1.0xx10^(15)Hz, lambda=6328Å` corresponds to `v=4.7xx10^(14)Hz lt v_(0)`. The photo - cell will not respond howsoever high be the intensity of laster light.