Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): For an electromagnetic wave propagating in a non-magnetic medium with relative permittivity _r = 4

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Correct answer: D. Assertion (A) is false but Reason (R) is true

The speed of an electromagnetic wave in a medium is given by

v = \dfrac{c}{\sqrt{\mu_r \epsilon_r}}

.
For a non-magnetic medium, the relative permeability

\mu_r = 1

. Given

\epsilon_r = 4

, the speed of the wave is

v = \dfrac{c}{\sqrt{1 \times 4}} = \dfrac{c}{2}

.

The amplitudes of the electric and magnetic fields are related by

E_0 = v B_0

.
Substituting the value of

v

, we get

E_0 = \left(\dfrac{c}{2}\right) B_0

, which gives

B_0 = \dfrac{2E_0}{c}

.

The Assertion incorrectly states that

B_0 = \dfrac{E_0}{2c}

. The Reason correctly states the standard formulas for wave speed and the amplitude relation. Therefore, Assertion (A) is false but Reason (R) is true.

Answer: Assertion (A) is false but Reason (R) is true

Given below are two statements: one is labelled as Assertion (A)...

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