Question

Light with a wavelength of 5.0 · 10-7 m strikes a surface that requires 2.0 EV to eject an electron. Calculate the energy, in electron volts, of one incident photon._____ eV6.9 x 10 -302.52.5 x 10 -306.2 x 10 -13

Answer 1

Given data:

* The wavelength of the incident light is,

$\lambda=5\times10^{-7}\text{ m}$

Solution:

The energy of the incident photon is,

$E=\frac{hc}{\lambda}$

where h is a planck's constant, and c is the speed of light,

Substituting the known values.

$E=\frac{6.626\times10^{-34}\times3\times10^8}{5\times10^{-7}}$

By calculations,

$\begin{gathered} E=4\times10^{-19}\text{ J} \\ E=\frac{4\times10^{-19}}{1.6\times10^{-19}} \\ E=2.5\text{ eV} \end{gathered}$

Thus, the energy of an incident photon is 2.5 eV.

Hence, second option is the correct answer.