Posted by **Sandhya** on Friday, April 17, 2009 at 10:51pm.

Cosmic microwave background radiation fills all space with an average energy density of 4 x 10^-14 j/m^3.(a) Find the rms value of electric field associated with this radiation.(b) How far from a 7.5 kW radio transmitter emitting uniformly in all direction would you find a comparable value?

- Physics -
**drwls**, Friday, April 17, 2009 at 11:02pm
There is a formula that relates radiation energy density to the E-field strength.

Get to know it.

Energy density = (1/2) epsilono * E^2

For an electromagnetic wave, there is an equal amount of energy in the magnetic field, as I recall.

For the E-field energy density at a distance R from that transmitter,

divide the radiated power by 4 pi R^2. That is the rate that energy is radiated away. Half of that power is due to the E-field. Divide by c for the E-field energy density. Set equal to the part (a) value and solve for R

## Answer this Question

## Related Questions

- Physics - If the cosmic microwave background radiation (CMBR) is at a ...
- chemistry - Which of the following statements about UV radiation is/are FALSE? (...
- Astronomy - If the cosmic microwave background radiation (CMBR) is at a ...
- Astronomy - If the cosmic microwave background radiation (CMBR) is at a ...
- chemistry - A microwave oven heats by radiating food with microwave radiation ...
- chemistry - A microwave oven heats by radiating food with microwave radiation ...
- CHEMISTRY - I don't even understand how this question works. How do I solve it? ...
- Chemistry - 27. Excess exposure to nuclear radiation can cause harm. All of the ...
- physics - a radiation survey meter observed gamma radiation of 150 mR/hr. The ...
- Chemistry! - Hey jiskha. Microwave ovens emit microwave radiation that is ...

More Related Questions