Question

A typical small helium-neon laser (λ=632.8μm) has a continuous output power of 3.00mW and a beam...

A typical small helium-neon laser (λ=632.8μm) has a continuous output power of 3.00mW and a beam diameter of 2.00mm.

a. What is the average value of the electric field's amplitude within the beam?

b. How many photons are emitted each second by the laser?

Homework Answers

Answer #1

b)

The energy of a photon is given by the equation E = hc/λ,

where E is the energy,

Planck's constant h = 6.63 x 10-34

speed of light c = 3 x 108 m/s and λ is the wavelength of the light (in metres).
given λ=632.8x10-6 m

then the energy of one photon is

E=hc/λ

=(1.989x10-25)/(632.8x10-6)

E=3.14x10-22 J

3mW=0.003 j/s

So the photons are emitted each second by the laser is

=(0.003)/(3.14x10-22)

=9.5x1018

a)
average value =E(Δx)

diameter =0.02m

=(3.14x10-22)x(0.02)

=6.28x10-24

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