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Dmitrij [34]
3 years ago
12

How many photons strike the cd surface during the playing of a cd 69 minutes in length?

Physics
1 answer:
Reptile [31]3 years ago
8 0

Answer:

Photons strike the CD n=1.624 x10^{18}

Explanation:

First of all, it is necessary to calculate the energy produced by a semiconductor laser for 69 minutes:

69minutes*\frac{60s}{1 minute}=4140s

E=0.1x10^{-3}w*4140s=0.414J

Next, it is possible to calculate the number of photons striking the CD surface during this time:

E=\frac{n*h*c}{l}

l=780x10^{-9}m long in CD

c=3x10^8 m/s light velocity

h=6.626x10^{-34} J*s

Solve to n'

n=\frac{E*l}{c*h}=\frac{0.414 J*780x10^{-9}m}{3x10^8m/s*6.626x10^{-34}}

n=1.624 x10^{18}

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