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JEE MAIN 2024
01-02-2024 S2
Question
Monochromatic light of frequency $6 \times 10^{14}$ Hz is produced by a laser. The power emitted is $2 \times 10^{-3} \mathrm{~W}$ W. How many photons per second on an average, are emitted by the source ? (Given h=$6.63 \times 10^{-34} \mathrm{Js}$ )
Select the correct option:
A
$9 \times 10^{18}$
B
$6 \times 10^{15}$
C
$5 \times 10^{15}$
D
$7 \times 10^{16}$
✓ Correct! Well done.
✗ Incorrect. Try again or view the solution.
Solution
$\begin{aligned} & \mathrm{P}=\operatorname{nh} v \\ & \mathrm{n}=\frac{\mathrm{P}}{\mathrm{h} v}=\frac{2 \times 10^{-3}}{6.63 \times 10^{-34} \times 6 \times 10^{14}} \\ & =5 \times 10^{15}\end{aligned}$
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