Question

The energy of a photon is $ 3\times {{10}^{-12}}\text{erg}\text{.} $ What is its wavelength in nm? $ (h=6.62\times {{10}^{-27}}erg\,-s;c=3\times {{10}^{10}}cm/s) $

• A. 662
• B. 1324
• C. 66.2
• D. 6.62

Answer 1

Answer: (A)

$ E=3\times {{10}^{-12}}\text{erg} $
$ \lambda =? $
$ h=6.62\times {{10}^{-27}}erg-s $
$ c=3\times {{10}^{10}}cm\,{{s}^{-1}} $
$ E=\frac{hc}{\lambda } $
$ 3\times {{10}^{-2}}=\frac{6.62\times {{10}^{-27}}\times 3\times {{10}^{10}}}{\lambda } $
$ \lambda =\frac{6.62\times {{10}^{-27}}\times 3\times {{10}^{10}}}{3\times {{10}^{-12}}} $
$ =6.62\times {{10}^{-5}}\,cm $
$ =662\times {{10}^{-7}}\,cm $
$ =662\times {{10}^{-9}}m=662\,nm $