How much energy is transported by an EM wave with a given E field strength?

In summary, an EM wave with an E field of 36.5 mV/m can transport energy across a 1.15 cm^2 area per hour.
  • #1
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Homework Statement


How much energy is transported across a 1.15 cm^2 area per hour by an EM wave whose E field has an rms strength of 36.5 mV/m?

Homework Equations



E=hv?
The big problem I'm having is that I don't know what formulae to use.

The Attempt at a Solution


I know what V/m = J/C = J/(A*s) and I know I need to get to J/h. But I don't know what I have that would include Amps or Coloumbs to get rid of that part (I've resorted to trying to sort out units in the face of the lack of equations.

Thanks!
 
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  • #2
Queue said:

Homework Statement


How much energy is transported across a 1.15 cm^2 area per hour by an EM wave whose E field has an rms strength of 36.5 mV/m?

Homework Equations



E=hv?
The big problem I'm having is that I don't know what formulae to use.

The Attempt at a Solution


I know what V/m = J/C = J/(A*s) and I know I need to get to J/h. But I don't know what I have that would include Amps or Coloumbs to get rid of that part (I've resorted to trying to sort out units in the face of the lack of equations.

Thanks!

Ok, I have from my book (which was just returned to me) that energy in a wave is given by \epsilon_0 E2 with units of J/m3. So I have u = 8.85*10-12*(36.5*10-3)2. From there I divided by the area I am given (1.15 cm2) and then multiplied by the speed of light (in hours) to give me the right units but my answer was incorrect according to mastering physics. Perhaps I made a math error or perhaps I'm having conceptual issue. Any help would be appreciated.
 
  • #3
I think you did it correctly, but I'll just ask if you converted the area to m2 units
 
  • #4
I did convert to square meters.

I multiplied by area, didn't divide like I thought I was supposed to which actually makes my units work out.

This gives me u = [tex]\epsilon_0 E^2[/tex] = 8.85*10-12*(3.65*103)2 J/(m3). From there I have u*A = 8.85*10-12*(3.65*103)2*0.000115 J/m. Then I multiplied by c giving u*A*c = 8.85*10-12*(3.65*103)2*0.000115*3*109 = whatever it is J/s. Then I just multiplied by 3600 (seconds per hour) to get J/h.

Thanks!
 
Last edited:

What is energy from an EM wave?

Energy from an EM wave refers to the transfer of electromagnetic energy through the oscillation of electric and magnetic fields. This energy travels through space in the form of waves at the speed of light.

How is energy from an EM wave created?

Energy from an EM wave is created when an electrically charged particle, such as an electron, is accelerated. This acceleration creates a disturbance in the electric and magnetic fields, resulting in the formation of an EM wave.

What are the different types of energy from EM waves?

There are two main types of energy from EM waves: electric energy and magnetic energy. Electric energy is associated with the oscillations of electric fields, while magnetic energy is associated with the oscillations of magnetic fields.

What are some examples of energy from EM waves?

Some common examples of energy from EM waves include light, radio waves, microwaves, x-rays, and gamma rays. These waves are used in various technologies, such as communication systems, medical imaging, and energy production.

How is energy from an EM wave measured?

The energy from an EM wave is measured in terms of its frequency and wavelength. The higher the frequency of the wave, the more energy it carries. Wavelength is inversely proportional to frequency, so shorter wavelengths have higher energy than longer wavelengths.

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