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# The energy of photon of electromagnetic radiation of wavelength = $2000\: A^{\circ}$ is:

$\begin {array} {1 1} (a)\;1.76 \times 10^{-18}J & \quad (b)\; 0.99 \times 10^{-18} J \\ (c)\;0.54 \times 10^{-18}J & \quad (d)\;0.63 \times 10^{-18}J \end {array}$

Energy, $E = \large\frac{hc}{\lambda}$
$=\large\frac{ 6.6 \times 10^{-34} \times 3 \times 10^8 }{(2000 \times 10^{-10} ) }$$= 0.99 \times 10^{-18} J$
Ans : (b)