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A source of monochromatic radiation of wavelength $400 \mathrm{~nm}$ provides $1000 \mathrm{~J}$ of energy in 10 seconds. When this radiation falls on the surface of sodium, $x \times 10^{20}$ electrons are ejected per second. Assume that wavelength $400 \mathrm{~nm}$ is sufficient for ejection of electron from the surface of sodium metal. The value of $x$ is________
(Nearest integer)
$\left(\mathrm{h}=6.626 \times 10^{-34} \mathrm{Js}\right)$
Total energy provided by
Source per second $=\frac{1000}{10}=100 \mathrm{~J}$
Energy required to eject electron $=\frac{h c}{\lambda}$
$=\frac{6.626 \times 10^{-34}}{400 \times 10^{-9}} \times 3 \times 10^{8}$
Number of electrons ejected
$=\frac{100}{\frac{6.626 \times 10^{-34} \times 3 \times 10^{8}}{400 \times 10^{-9}}}$
$=\frac{400 \times 10^{-7} \times 10^{26}}{6.626 \times 3}$
$=\frac{40 \times 10^{-20}}{6.626 \times 3}$
$=2.01 \times 10^{20}$
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