Question

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

Answer 1

Photons strike the CD
`n=1.624 x10^(18)`

Step-by-step explanation:

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

`69minutes*(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=(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=(E*l)/(c*h)=(0.414 J*780x10^(-9)m)/(3x10^8m/s*6.626x10^(-34))`

`n=1.624 x10^(18)`