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 × 10⁸
• B. 3.33 × 10^–9
• C. 9.1 × 10^–31
• D. 6.64 × 10^–34

Answer 1

Answer: (B)

3.33 × 10^–9

Answer 2

$\lambda = \frac{h}{p}$ (for electron) or $p = \frac{h}{\lambda}$ and

$E = \frac{hc}{\lambda}$ (for photon)

∴ $\frac{p}{E} = \frac{1}{c} = \frac{1}{3 \times 10^{8}m/s} = 3.33 \times 10^{- 9}s/m$