If the wavelength of an electromagnetic radiation is $2000 Ã…$, what is its energy in ergs?

If the wavelength of an electromagnetic radiation is $2000 Ã…$, what is its energy in ergs?
  1. $9.94 \times 10^{-12}$
  2. $9.94 \times 10^{-19}$
  3. $4.97 \times 10^{-12}$
  4. $4.97 \times 10^{-19}$

Solution

$E=h v, v=\frac{3 \times 10^{10}}{2000 \times 10^{-8}}=1.5 \times 10^{15} \sec ^{-1}$ $h=6.6 \times 10^{-27}$ erg sec $E=h v=6.6 \times 10^{-27} \times 1.5 \times 10^{15}=9.94 \times 10^{-12} \mathrm{erg}$

Asked in: AP EAMCET 2003

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