Problem: The watt is the derived SI unit of power, the measure of energy per unit time: 1W = 1J/s. A semiconductor laser in a CD player has an output wavelength of 780 nm and a power level of 0.10 mW.How many photons strike the CD surface during the playing of a CD 69 minutes in length?

FREE Expert Solution

We’re being asked to determine the number of photons that strike the CD surface during the playing of a CD in a length of 69 minutes.


Recall that the energy of a photon (E) is given by:


E=hv (1)


where:

h = Planck’s constant (6.626 × 10–34 J • s)

v = frequency (in s–1)


Also, recall that the frequency (v) and wavelength (λ) are related:


λ=cv (2)


where:

c = speed of light (3.0 × 108 m/s)


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Problem Details

The watt is the derived SI unit of power, the measure of energy per unit time: 1W = 1J/s. A semiconductor laser in a CD player has an output wavelength of 780 nm and a power level of 0.10 mW.

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

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What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the The Particle Nature of Light concept. You can view video lessons to learn The Particle Nature of Light. Or if you need more The Particle Nature of Light practice, you can also practice The Particle Nature of Light practice problems.