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11.Dual Nature of Radiation and matter
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If $5\%$ of the energy supplied to a bulb is irradiated as visible light, how many quanta are emitted per sec by a $100$ $watt$ lamp ? Assume wavelength of visible light as $5.6\times10^{-5}\, cm$.
A
$1.4\times10^{19}$
B
$2.0\times10^{-4}$
C
$1.4\times10^{-19}$
D
$2.0\times10^{4}$
Solution
Energy radiated as visible light
$=\frac{5}{100} \times 100=5 \mathrm{\,J} / \mathrm{s}$
Let $n$ be the number of photons emitted per sec
Then
$\mathrm{nhv}=\mathrm{n} \frac{\mathrm{hc}}{\lambda}=5$
$\therefore \quad \mathrm{n}=\frac{5 \lambda}{\mathrm{hc}}=\frac{5 \times 5.6 \times 10^{-7}}{\left(6.6 \times 10^{-34}\right)\left(3 \times 10^{8}\right)}=1.4 \times 10^{19}$
Standard 12
Physics
