An electromagnetic wave is incident from vacuum normally on a planar surface of a non-magnetic medium. If the amplitude of the electric field of the incident wave is E, and that of the transmitted wave is 2E₀/3, then neglecting any loss, the refractive index of the medium is

Correct option is B

Concept:
The transmission coefficient  (T ) for an electromagnetic wave moving from a vacuum into a medium with refractive index ( n ) is given by: ​$$\\T = \frac{2n_1}{n_1 + n_2} \\$$​​
This coefficient ( T ) is also expressed as the ratio of the amplitude of the transmitted wave (E_t) to the amplitude of the incident wave (E₀): ​$$\\ T = \frac{E_t}{E_0} \\$$​​
Solution:
The refractive index of the vacuum is: ( n₁ = 1 )
In the problem, it states that $$\\E_t = \frac{2E_0}{3} \\$$​​
Substituting the value in the formula for the coefficient of transmission ( T ):
​$$\\ \frac{2}{3} = \frac{2n_1}{n_1 + n_2} \\\\ \frac{2}{3} = \frac{2}{1 + n_2} \\\\ \frac{1}{3} = \frac{1}{1 + n_2} \\$$​​
Thus, 1+n₂ = 3

∴ n₂ = 2