How many photons are emitted by a laser source of 5 × 10^{-3} ,W operating at 632.2 ,nm in 2 ,s is

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11.Dual Nature of Radiation and matter

easy

How many photons are emitted by a laser source of $5 \times 10^{-3} \,W$ operating at $632.2 \,nm$ in $2 \,s$ is .......$\times 10^{16}$ $\left(h=6.63 \times 10^{-34} \,Js \right)$

A

$3.2$

B

$1.6$

C

$4$

D

$0.4$

Solution

(a)

Number of photons per second $=\frac{\text { Total energy emitted/sec }}{\text { Energy of one photon }}$

Energy of one photon $=\frac{h c}{\lambda}=\frac{h c}{632.2 \times 10^{-9}}$

Energy per second emitted $=5 \times 10^{-3} \,W$

Total number of photons $=$ Photons emitted per second $\times$ Time

When time $=2 \,s$

Standard 12

Physics

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