The electric field of a plane electromagnetic wave, travelling in an unknown nonmagnetic medium is given by, Ey = 20 sin (3 × 10⁶ x - 4.5 × 10¹⁴ t) V/m (where x, t and other values have S.I. units). The dielectric constant of the medium is ______ (speed of light in free space is 3 × 10⁸ m/s) Numerical answer type. Work it out, then open the answer.

Answer: 4. v = ω/k = 4.5 × 10¹⁴3 × 10⁶ = 1.5 × 10⁸ m/s n = c/v = 2 Non-magnetic: K = n² = 4 So the answer is 4.

The electric field of a plane electromagnetic wave, travelling in an… | JEE Main 2026 (22 Jan, Shift 1)

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Speed of EM Waves in a Medium

The electric field of a plane electromagnetic wave, travelling in an unknown nonmagnetic medium is given by,

$E_y = 20 \sin\left(3 \times 10^{6} x - 4.5 \times 10^{14} t\right)\text{ V/m}$

(where $x, t$ and other values have S.I. units). The dielectric constant of the medium is ______ (speed of light in free space is $3 \times 10^{8}\text{ m/s}$ )

Numerical answer type. Work it out, then open the answer.

Show answer and solution

Answer: 4

$v = \omega/k = \dfrac{4.5 \times 10^{14}}{3 \times 10^{6}} = 1.5 \times 10^{8}$ m/s
$n = c/v = 2$
Non-magnetic: $K = n^2 = 4$
So the answer is 4.

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