Question

A photon of wavelength 6630 k is incident on a totally reflecting surface. The momentum delivered by the photon is equal to

• A. $ 6.63\times {{10}^{-27}}k{{g}^{-}}m/s $
• B. $ 2\times {{10}^{-27}}k{{g}^{-}}m/s $
• C. $ {{10}^{-27}}k{{g}^{-}}m/s $
• D. None of the above

Answer 1

Answer: (B)

$ P=n\left( \frac{E}{t} \right) $ $ 10\,kWh=n\left[ \frac{200\,MeV}{t} \right] $ $ 10\times {{10}^{3}}\times 60\times 60=n\times 200\times {{10}^{6}}\times 1.6\times {{10}^{-19}} $ $ (\because \,t=1) $ $ n=\frac{10\times {{10}^{3}}\times 60\times 60}{200\times {{10}^{6}}\times 1.6\times {{10}^{-19}}} $ $ n=\frac{36\times {{10}^{19}}}{200\times 1.6} $ $ n=\frac{360\times {{10}^{18}}}{200\times 1.6} $ $ n=1.125\times {{10}^{18}} $ $ n=11.25\times {{10}^{17}} $