Question

The wavelength of a $1\, keV$ photon is $1.24 \times 10^{-9} m$. What is the frequency of $1 \,MeV$ photon?

• A. $ 1.24\times {{10}^{15}}Hz $
• B. $ 2.4\times {{10}^{20}}Hz $
• C. $ 1.24\times {{10}^{18}}Hz $
• D. $ 2.4\times {{10}^{24}}Hz $
• E. $ 2.4\times {{10}^{15}}Hz\text{ }, $

Answer 1

Answer: (B)

$ f=\frac{c}{\lambda }=\frac{c}{hc/E}=\frac{E}{h} $
$ \therefore $ $ f=\frac{1\times 1.6\times {{10}^{-13}}}{6.6\times {{10}^{-34}}}=2.4\times {{20}^{20}}Hz $