Electric field in a plane electromagnetic wave is given by E = 50 sin(500x - 10 × 1010 t) V/m The velocity of electromagnetic wave in this medium is: (Given C = speed of light in vacuum) (a) 3/2 C (b) C (c) 2/3 C (d) C/2

Answer: (c). Compare with E₀sin (kx - ω t): k = 500 m ⁻¹, ω = 10 × 10¹⁰ rad/s. v = (ω)/(k) = 10¹¹500 = 2 × 10⁸ m/s. v/C = 2 × 10⁸3 × 10⁸ = 2/3. So the answer is (c) 2/3C.

Electric field in a plane electromagnetic wave is given by E = 50… | JEE Main 2021 (27 Aug, Shift 1)

Q16JEE Main 2021 · 27 AUG · SHIFT 1Easy

Speed of EM Waves in a Medium

Electric field in a plane electromagnetic wave is given by E = 50 sin(500x $-$ 10 $\times$ 1010 t) V/m The velocity of electromagnetic wave in this medium is:

(Given C = speed of light in vacuum)

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Answer: (c)

Compare with $E_0\sin(kx - \omega t)$ : $k = 500$ m $^{-1}$ , $\omega = 10 \times 10^{10}$ rad/s.
$v = \dfrac{\omega}{k} = \dfrac{10^{11}}{500} = 2 \times 10^{8}$ m/s.
$\dfrac{v}{C} = \dfrac{2 \times 10^{8}}{3 \times 10^{8}} = \dfrac{2}{3}$ .
So the answer is (c) $\dfrac{2}{3}C$ .

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Speed of EM Waves in a Medium question from JEE Main 2021 (27 Aug, Shift 1)

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