JEE Main & Advanced Physics Photo Electric Effect, X- Rays & Matter Waves Question Bank Topic Test - Photo Electric Effect, X-Rays & Matter Waves

Light of wavelength 4000 Å falls on a photosensitive metal and a negative 2V potential stops the emitted electrons. The work function of the material (in eV) is approximately \[(h=6.6\times {{10}^{-34}}Js,\ \ e=1.6\times {{10}^{-19}}C,\ \ c=3\times {{10}^{8}}m{{s}^{-1}})\]

A) 1.1

B) 2.0

C) 2.2

D) 3.1

Correct Answer: A

Solution :

[a] Energy of incident light \[E\,(eV)=\frac{12375}{4000}=3.09\,eV\]

Stopping potential is 2V so \[{{K}_{\max }}=2\,eV\]

Hence by using \[E={{W}_{0}}+{{K}_{\max }}\]; W0\[=1.09\,eV\]\[\approx \,1.1\,eV\]