Question
Calculate the mass of photon with wavelength 5pm.
✓
Answer
$\mathrm{m}=?$
$\mathrm{C}=\text { velocity of photon }$
$=\text { velocity of light }=3 \times 10^8 \mathrm{~ms}^{-1}$
$\lambda=5\text{pm}=5\times10^{-10}\text{m}$
using de Broglie equation,
$\lambda=\frac{\text{h}}{\text{mc}}$
$5\times10^{-10}=\frac{6.626\times10^{-34}\text{Js}^{-1}}{\text{m}\times3\times10^8\text{ms}^{-1}}$
$\text{m}=\frac{6.626\times10^{-34}}{5\times10^{-10}\times3\times10^8}$
$=\frac{6.626}{15}\times10^{-34+10-8}=\frac{6.626\times10^{-32}}{15}$
$\text{m}=\frac{66.26}{15}\times10^{-33}\text{kg}$
$=4.417\times10^{-33}\text{kg}$
$\mathrm{C}=\text { velocity of photon }$
$=\text { velocity of light }=3 \times 10^8 \mathrm{~ms}^{-1}$
$\lambda=5\text{pm}=5\times10^{-10}\text{m}$
using de Broglie equation,
$\lambda=\frac{\text{h}}{\text{mc}}$
$5\times10^{-10}=\frac{6.626\times10^{-34}\text{Js}^{-1}}{\text{m}\times3\times10^8\text{ms}^{-1}}$
$\text{m}=\frac{6.626\times10^{-34}}{5\times10^{-10}\times3\times10^8}$
$=\frac{6.626}{15}\times10^{-34+10-8}=\frac{6.626\times10^{-32}}{15}$
$\text{m}=\frac{66.26}{15}\times10^{-33}\text{kg}$
$=4.417\times10^{-33}\text{kg}$
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