If photoelectrons emitted by a metl on irradiating it by a light of wave length `lamda` cannot move away farther than a distance 'd' in presence of a retarding electric field E, find threshold wavelength of the metal.

Options

A. `lamdac//eEd`
B. `lamda+(hc)/(eEd)`
C. `lamda-(hc)/(eEd)`
D. `[(1)/(lamda)-(eEd)/(hc)]^(-1)`

Answer

D

Explanation

`(hc)/(lamda)-(hc)/(lamda_(0))=eEd`
on solving we get `(1)/(lamda_(0))=(1)/(lamda)-(eEd)/(hc)`