Question

Assume the amplitude of the electric field in a plane electromagnetic wave is E1 and the amplitude of the magnetic field is B1. The source of the wave is then adjusted so that the amplitude of the electric field doubles to become 2E1. (i) What happens to the amplitude of the magnetic field in this process? It becomes four times larger. It becomes two times larger. It can stay constant. It becomes one-half as large. It becomes one-fourth as large. (ii) What happens to the intensity of the wave? It becomes four times larger. It becomes two times larger. It can stay constant. It becomes one-half as large. It becomes one-fourth as large. Need Help?

Answer 1

The amplitude of the magnetic field gets 2 times larger as well. The amplitudes are always directly proportional.

The intensity becomes four times as large. The intensity of any wave is always proportional to the square of its amplitude. So if the electric and magnetic field had gotten 3 times larger, the intensity would have become 9 times larger.

Answer 2

Answer:

I) It becomes two times larger

II) It becomes four times larger

Explanation:

I) Electric field is directly proportional to Magnetic field and as such, if one is increased, the other is also increased by the same proportion.

The formula is given as

$E_{1}  = cB_{1}$

c = speed of light, therefore

$2E_{1}  = c2B_{1}$

II) Intensity of is proportional to the square of amplitude, as such

If amplitude is doubled ($X2^{2}$), intensity is $X4^{}$

This means the intensity becomes four times bigger.