Question

The maximum wavelength of radiation that can produce photoelectric effect in a certain metal is $200nm$. The maximum kinetic energy acquired by electron due to radiation of $100nm$ wavelength will be

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

Answer 1

The correct option is B $6.2eV$

Incident energy ($E)=\frac{hc}{\lambda }$, where $\lambda =100nm$
Work function ($\varphi )=\frac{hc}{{\lambda }_0}$, where ${\lambda }_0=200nm$
Now,
$K.E_{max}=E-\varphi$
$\Rightarrow K.E_{max}\left(ineV\right)=\frac{hc}{e}(\frac{1}{\lambda }-\frac{1}{{\lambda }_0})$
=$\frac{6.626\times {10}^{-34}\times 3\times {10}^8}{1.6\times {10}^{-19}}(\frac{1}{100nm}-\frac{1}{200nm})K.E_{max}\left(ineV\right)=6.2$