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8.Electromagnetic waves
easy
The photon energy in units of $eV$ for electromagnetic wave of wavelength $2\,cm$ is
A
$2.5 \times 10^{-19}$
B
$5.2 \times 10^{16}$
C
$3.2 \times 10^{-16}$
D
$6.2 \times 10^{-5}$
Solution
As $ \mathrm{E} =\frac{\mathrm{hc}}{\lambda} $
$=\frac{6.6 \times 10^{-34} \times 3 \times 10^{8}}{2 \times 10^{-2}}=9.9 \times 10^{-24} \mathrm{\,J}$
$=\frac{9.9 \times 10^{-24}}{1.6 \times 10^{-19}} \mathrm{\,eV}=6.2 \times 10^{-5} \mathrm{\,eV} $
Standard 12
Physics
