In an experiment on photo electric emission, following observations were made,
(i) Wavelength of the incident light `=1.98xx10^(-7)m`,
(ii) Stopping potential `=2.5 "volt"`.
Find: (a) Kinetic energy of photoelectrons with maximum speed.
(b) Work function and
(c )Threshold frequency,

Explanation

(a) Since `V_(s)=2.5V`, `K_(max)=eV_(s)` so, `K_(max)=2.5 eV`
(b) Energy of incident photon
`E=(12400)/(1980)eV=6.26 eV` , `W=E-K_(max)=3.76 eV`
(c ) `hv_(th)=W=3.76xx1.6xx10^(-19)J :. v_(th)=(3.76xx1.6xx10^(-19))/(6.6xx10^(-34))~~9.1xx10^(14)Hz`