Calculate the velocity of a photo-electron, if the work function of the target material is 1.24 eV and the wavelength of incident light is `4360Å`. What retarding potential is necessary to stop the emission of the electrons?

Options

A. 1.6 V
B. 1.2 V
C. 2.8 V
D. 13.2 V

Answer

A

Explanation

Energy of photon , `E = hupsilon = (hc)/lamda`
or `E = (1240 eV nm) / (436 nm) = 2. 84 eV`
According to Einstein equation for photoelectric effect
`K_(max) = hupsilon_(0) - phi_(0) = 2.84 - 1.24 = 16 eV`
In terms of stopping potential
`K_(max) = eVs, 1.6 eV = eV_(s) , " or " V_s = 1.6 V`