An electromagnatic wave is traveling in vacuum with frequency 5.7 x 10 14 Hz. Th

Question

An electromagnatic wave is traveling in vacuum with frequency 5.7 x 1014 Hz. The wave has average total energy density of 4.9 x 10-6 J/m3.(a) What is the speed of this wave?

v =  m/s     

(b) What is the wavelength of this wave?

l =  m     

(c) What is the maximum electric field of this wave?

Emax =  V/m     

(d) What is the rms magnetic field of this wave?

Brms =  T     

(e) How much energy does a 1.9 m2 flat surface (perpendicular to the wave propagation direction) receive in 7 s?

E =  J     

(f) How long does it take for this wave to travel from the sun to the earth?

t =  min     

(g) How many wavelengths of the wave fit in this distance?

N =  wavelengths

Explanation / Answer

I am allowed to answer only 4 parts at a time.

a)
speed of electromagetic wave in vacuum = 3*10^8 m/s

b)
use:
wavelength = speed / f
= (3*10^8) / (5.7*10^14)
= 5.263*10^-7 m
Answer: 5.263*10^-7 m

c)
Energy density = 0.5*ebsoleneo*E^2
4.9*10^-6 = 0.5*(8.854*10^-12)*E^2
E = 1052.1 V/m
this is Erms
Emax = Erms * sqrt(2)
= 1052.1 * sqrt(2)
= 1487.8 V/m
Answer: 1487.8 V/m

d)
Brms = Erms / c
= 1052.1 / (3*10^8)
= 3.51*10^-6 T
Answer: 3.51*10^-6 T

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