Question

$\text{ The electric field of an EM wave in free space is given by } E = 10 \cos(10^7 t + kx) \, \hat{j} \, \text{V/m, where } t \text{ and } x \text{ are in seconds and meters, respectively. It can be inferred that:}$
Which of the following pairs of statements are correct:
(A) Wavelength λ is 188.4 m,
(B) Wave number k is 0.33 rad/m,
(C) Wave amplitude is 10 V/m,
(D) Wave is propagating along +x-direction.

• A. (C) and (D)
• B. (A) and (B)
• C. (B) and (C)
• D. (A) and (C)

Answer 1

Answer: (A)

(C) and (D)

Answer 2

The electric field of the wave has amplitude 10 V/m, which confirms that (C) is correct. Since the wave equation includes kx, the wave propagates along the +x-axis, confirming (D). Thus, the correct answer is (C) and (D).