CUET · PHYSICS · PYQ PAPER 2025

A plane electromagnetic wave of frequency 50 MHz travels in free space in the X- direction. At a particular point in space and time, the magnetic field is 0.003 G in the Z-direction. The magnitude and direction of the electric field is

A 9 V/m, along the negative Y-direction
B \( 1 \times 10^{-15} \) V / m along the Y-direction
C 90 V/m along the Y-direction
D \( 1 \times 10^{15} \) V / m along the Y-direction

Verified Solution

Answer & Solution

Correct Answer

(C) 90 V/m along the Y-direction

Step-by-step Solution

Detailed explanation

\( B = 0.003 \text{ G} = 0.003 \times 10^{-4} \text{ T} = 3 \times 10^{-7} \text{ T} \) \( E = cB = (3 \times 10^8 \text{ m/s}) \times (3 \times 10^{-7} \text{ T}) = 90 \text{ V/m} \) For propagation in X-direction (\( \hat{i} \)) and \( \vec{B} \) in Z-direction (…

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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