Question

If a photon has a momentum of $P=2\times {10}^{-27}\text{kg-m/s}$, find the energy associated with the photon.

• A. $12.56\text{eV}$
• B. $6\text{eV}$
• C. $3.14\text{eV}$
• D. $3.75\text{eV}$

Answer 1

The correct option is D $3.75\text{eV}$

The energy and momentum of a photon are related as,
$E=pc$
$E=2\times {10}^{-27}\times 3\times {10}^8\text{J}$
$E=6\times {10}^{-19}\text{J}$

But options are in eV.
$\therefore E=\frac{6\times {10}^{-19}}{1.6\times {10}^{-19}}=3.75\text{eV}$

Hence, $\left(D\right)$ is the correct answer.

$\begin{array}{c}\text{Why this question?}\\ \text{A typical formula based numerical}E=pc\text{. Also the conversion of}\text{J}\text{to}\text{eV}\text{.}\end{array}$