Question

An electromagnetic wave has an electric firled with peak value 120 n/c. What is the average energy delivered to a surface with area 2. 25 m^2 by this wave in 3 hours?

Answer 1

The average energy delivered to a surface is 7.5*10^6J.

To find the answer, we have to know about the poynting vector.

How to find the average energy delivered to a surface?

• Energy per time through a unit area perpendicular to the direction of propagation of EM wave is called poynting vector.
• We can write the expression of Poynting vector as,

                               $S=E_{avg}*c$

where; E(avg) is the average energy of the EM wave, and c is the speed of light.

• We can rewrite the expression as per our defenition as,

                            $\frac{E*A}{t}=E_{avg}*c$

• Thus, the value of average energy will be,

                   $E_{avg}= \frac{E*A*c}{t} =\frac{120*2.25*3*10^8}{3*60*60s} =7.5*10^6J$

Thus, we can conclude that, the average energy delivered to a surface is 7.5*10^6J.

Learn more about the poynting vector here:

brainly.com/question/19530841

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