The energy of a photon is $3 \times 10^{-12}$ ergs. What is its wavelength in $\mathrm{nm}$ ? $\text { ( }…

The energy of a photon is $3 \times 10^{-12}$ ergs. What is its wavelength in $\mathrm{nm}$ ? $\text { ( } h=6.62 \times 10^{-27} \text { ergs-s; } c=3 \times 10^{10} \mathrm{~cm} / \mathrm{s} \text { ) }$
  1. 662
  2. 1324
  3. 66.2
  4. 6.62

Solution

$E=3 \times 10^{-12}$ ergs. $\lambda=$ ? $h=6.62 \times 10^{-27}$ erg-s $c=3 \times 10^{10} \mathrm{cms}^{-1}$ $E=\frac{h c}{\lambda}$ $3 \times 10^{-2}=\frac{6.62 \times 10^{-27} \times 3 \times 10^{10}}{\lambda}$ $\lambda=\frac{6.62 \times 10^{-27} \times 3 \times 10^{10}}{3 \times 10^{-12}}$ $=6.62 \times 10^{-5} \mathrm{~cm}$ $=662 \times 10^{-7} \mathrm{~cm}$ $=662 \times 10^{-9} \mathrm{~m}$ $=662 \mathrm{~nm}$

Asked in: AP EAMCET 2006

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