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Question: Monochromatic light of frequency \(6 \times 10^{14}Hz\)is produced by a laser. The power emitted is ...

Monochromatic light of frequency 6×1014Hz6 \times 10^{14}Hzis produced by a laser. The power emitted is 2×10−3W.2 \times 10^{- 3}W. The number of photons emitted per second is (Given h=6.63×10−34Js6.63 \times 10^{- 34}Js)

A

2×10152 \times 10^{15}

B

3×10153 \times 10^{15}

C

4×10154 \times 10^{15}

D

5×10155 \times 10^{15}

Answer

5×10155 \times 10^{15}

Explanation

Solution

: Here υ=6×1014Hz,h=6.63×10−34js\upsilon = 6 \times 10^{14}Hz,h = 6.63 \times 10^{- 34}js

As E=hυ=6.63×10−34×6×1014E = h\upsilon = 6.63 \times 10^{- 34} \times 6 \times 10^{14}

=3.98×10−19j= 3.98 \times 10^{- 19}j

Number of photons emitted per second

n=pEn = \frac{p}{E}

=2×10−33.98×10−19=5×1015= \frac{2 \times 10^{- 3}}{3.98 \times 10^{- 19}} = 5 \times 10^{15}photons per second