If the frequency of a plane electromagnetic wave increases four times, the depth of penetration, when is incident normally on a good conductor will Select one:a. increases by a factor of 2b. decreases by a factor of 4c. decreases by a factor of 2d. remains same

To answer this question, we need to understand the relationship between the frequency of an electromagnetic wave and the depth of penetration in a good conductor.

When an electromagnetic wave is incident normally on a good conductor, it creates eddy currents within the conductor. These eddy currents oppose the flow of the electromagnetic wave, causing it to penetrate into the conductor to a certain depth.

Now, if the frequency of the electromagnetic wave increases four times, it means that the wave oscillates more rapidly. This increase in frequency affects the depth of penetration.

According to the skin effect, the depth of penetration is inversely proportional to the square root of the frequency. Mathematically, we can express this relationship as:

Depth of Penetration ∝ 1/√(Frequency)

If the frequency increases four times, we can substitute the new frequency value into the equation:

New Depth of Penetration ∝ 1/√(4 * Old Frequency)

Simplifying this equation, we get:

New Depth of Penetration ∝ 1/√(4) * 1/√(Old Frequency)

New Depth of Penetration ∝ 1/2 * 1/√(Old Frequency)

From this equation, we can see that the new depth of penetration is half of the old depth of penetration. Therefore, the correct answer is option c. The depth of penetration decreases by a factor of 2 when the frequency of the plane electromagnetic wave incident normally on a good conductor increases four times.