Question

What is the maximum value of the electric field in an electromagnetic wave whose average intensity is 7.45 W/m2 ?

Answer 1

Given data:

Average intensity of the em-field = 7.45 W/m²

We know that average intensity of the em-field is given by Poynting vector:

Where E is the electric field

B is the magnetic field

is the absolute permeability

In case of electromagnetic field the E and B are at right angles therefore

Therefore we get:

As , where c is the speed of light. Substituting this in above equation we get:

Rearranging above equation to calculate E we get:

Substituting the values we get:

Now the maximum value of E will be given by:

Which is the required answer

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