A small helium-neon laser emits red visible light with a power of 4.00 mW in a b

Question

A small helium-neon laser emits red visible light with a power of 4.00 mW in a beam that has a diameter of 1.60 mm.     (a) What are the amplitudes of the electric and magnetic fields of the light?      Emax = 1 V/m Bmax = 2 T
    (b) What are the average energy densities associated with the electric field and with the magnetic field?      uE,av = 3 J/m3 uB,av = 4 J/m3
    (c) What is the total energy contained in a 1.00-m length of the beam?
5 J . my first 2 answers in (a) are correct, please find (b) and (c)! Thanks.     (a) What are the amplitudes of the electric and magnetic fields of the light?      Emax = 1 V/m Bmax = 2 T
    (b) What are the average energy densities associated with the electric field and with the magnetic field?      uE,av = 3 J/m3 uB,av = 4 J/m3
    (c) What is the total energy contained in a 1.00-m length of the beam?
5 J . my first 2 answers in (a) are correct, please find (b) and (c)! Thanks. Emax = 1 V/m Bmax = 2 T

Explanation / Answer

(b) uE = 0.5 * 10^-9 / 4pi * 1224.7^2 /2

= 3 * 10^-5

uB = 0.5 * (4.08 * 10^-6)^2 / 2*4pi*9*10^-7

= 3.68 * 10^-5

(c) total energy = 6.68 * 10^-5 J

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