Question

Light described at a place by the equation $E=\left(100V/M\right)\times \left[sin\right(5\times {10}^{15}{s}^{-1})t+sin(8\times {10}^{15}{s}^{-1}\left)t\right]$
Falls on a metal surface having work function 2.0 e.V Calculate the maximum kinetic energy of the photoelectrons

• A. 3.27 eV
• B. 5 eV
• C. 1.27 eV
• D. 2.5 eV

Answer 1

The correct option is A 3.27 eV

Given that,

$E=\left(100V/m\right)\times \left[\sin \right(5\times {10}^{15}{s}^{-1})t+\sin (8\times {10}^{15}{s}^{-1}\left)t\right]$

Here, the light contains two different frequencies. The one with larger frequency will cause photoelectrons with largest kinetic energy. So the larger frequency is

$\nu =\frac{\omega }{2\pi }=\frac{8\times {10}^{15}}{2\pi }=1.27\times {10}^{15}Hz$

The maximum kinetic energy of photoelectrons is

$K_{max}=h\nu -W$

$=(4.13\times {10}^{-15}eVs)\times 1.27\times {10}^{15}-2$

$=5.245-2$

$=3.24eV$