Question

The maximum wavelength of light for photoelectric effect from a metal is $200nm$. The maximum kinetic energy of electron which is emitted by the radiation of wavelength $100nm$ will be:

• A. $12.4eV$
• B. $6.2eV$
• C. $100eV$
• D. $200eV$

Answer 1

The correct option is B $6.2eV$

Given that,

The maximum wave length ${\lambda }_0=200nm$

Radiation of wave length $\lambda =100nm$

We know that, the maximum K.E is

$K.E=12400[\frac{1}{\lambda }-\frac{1}{{\lambda }_0}]$

$K.E=12400[\frac{1}{1000}-\frac{1}{2000}]$

$K.E=12400\times \frac{1}{2000}$

$K.E=6.2eV$

Hence, the kinetic energy is $6.2eV$