Question

An electron and a photon have same wavelength. It p is the momentum of electron and E the energy of photon. The magnitude of p/ E in S.I. unit is

• A. $3.0\times {10}^8$
• B. $3.33\times {10}^{-9}$
• C. $9.1\times {10}^{-31}$
• D. $6.64\times {10}^{-34}$

Answer 1

The correct option is B $3.33\times {10}^{-9}$

$\lambda =\frac{h}{p}$ (for electron) or $p=\frac{h}{\lambda }$ and $E=\frac{hc}{\lambda }$ (for photon)
$\therefore \frac{P}{E}=\frac{1}{c}=\frac{1}{3\times {10}^{8}m/s}=3.33\times {10}^{-9}s/m$