Question

If work function to target material is 2.34 eV and wavelength of incident light is $4.36\times {10}^{-7}$ m then minimum potential required to stop the photo current is about :

$(h=6.6\times {10}^{-34}Js)$

• A. 1.5 V
• B. 0.5 V
• C. 3.5V
• D. Zero

Answer 1

Answer: (B)

0.5 V

Given,

Work function, $\varphi =2.34eV$

wavelength, $\lambda =4.36\times {10}^{-7}m$

Planck's constant,$h=6.6\times {10}^{-34}Js$

By Einstein photoelectric equation,

$K.E=\frac{hc}{\lambda }-\varphi$

$K.E=\frac{6.6\times {10}^{-34}\times 3\times {10}^{8}eV}{4.36\times {10}^{-7}\times 1.6\times {10}^{-19}}-2.34eV$

$K.E=2.838eV-2.34eV$

$K.E=0.5eV$

The kinetic energy is equal to $e{V}_0$

where, $V_0=$stopping potential

$e{V}_0=0.5eV$

$V_0=0.5V$

The correct option is B.