Question

in a photoelectric effect experiment the threshold wavelength of the light is $380nm$. If the wavelength of incident light is $260nm$, the maximum kinetic energy electrons will be:
Given $E\left(ineV\right)=\frac{1237}{\lambda \left(innm\right)}$

• A. $1.5eV$
• B. $4.5eV$
• C. $15.1eV$
• D. $3.0eV$

Answer 1

Answer: (A)

$1.5eV$

$K_{max}=\frac{hc}{\lambda }-\frac{hc}{{\lambda }_0}$

$\Rightarrow K_{max}=hc\left(\frac{{\lambda }_0-\lambda }{\lambda {\lambda }_0}\right)$

$\Rightarrow K_{max}=\left(1237\right)\left(\frac{380-260}{380\times 260}\right)$
$=1.5eV$