If electric field associated with an electromagnetic wave is given by E= 30 (0.2π × 10^-4 m^-1x -0.6π × 10^4 Hz t)j then the direction of propagation of the wave is along, (A) i (B) -i (C) k (D) -k

PhysicsCBSE Class 12 · Sample paper, session 2026-27 · 1 mark · MCQ

CBSE Class 12 Physics sample paper 2026-27: question 4

From the official CBSE sample question paper for 2026-27, section A, question 4, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q4 · 1 mark · MCQElectromagnetic Waves

If electric field associated with an electromagnetic wave is given by $E = 30 sin (0.2 π \times 1 0^{- 4} m^{- 1} x - 0.6 π \times 1 0^{4} Hz t) \hat{j}$ then the direction of propagation of the wave is along,

(A) $\hat{i}$
(B) $- \hat{i}$
(C) $\hat{k}$
(D) $- \hat{k}$

Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2026-27.

Hints

Open one hint at a time and try again before the next.

Hint 1

Which coordinate appears in the phase of the wave?

Hint 2

Look at the relative signs of the $x$ and $t$ terms.

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

The wave has the form $sin (k x - ω t)$ . A phase of this form describes a wave travelling in the $+ x$ direction.
½ mark
So the wave propagates along $\hat{i}$ . Option (A).
½ mark

Answer: $\hat{i}$ , option (A)

Where the marks are

Recognises the form $(k x - ω t)$ as propagation along $+ x$ (1 mark)

Revise the chapter

Chapter: Electromagnetic Waves (notes, formulas, where marks are lost and every past question)

Practise this chapterBoard-style questions from Electromagnetic Waves, one at a time, marked against the answer key and marking points.Back to the full paperSample paper 2026-27: every question, by section.

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CBSE Class 12 Physics sample paper 2026-27: question 4

Hints

Step-by-step solution

Revise the chapter

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