Question

A sinusoidal wave has an amplitude of 3cm. Time period is 1s. The wavelength is 1cm. And at x = 0, t=0 the particle is at its mean position & moving upwards. What is the equation of the wave if it is travelling along the positive x-axis?

(a) y = 3sin(2πx – 2πt)

(b) y = 3sin(2πt – 2πx)

(c) x = 3sin(2πt – 2πy)

(d) y = 3cos(π + 2πt – 2πx)

I got this question in an internship interview.

This key question is from Displacement Relation in a Progressive Wave topic in division Waves of Physics – Class 11

Answer 1

Correct answer is (b) y = 3sin(2πt – 2πx)

Explanation: The wave number k = 2π/1 = 2π.

The angular frequency w = 2π/1 = 2π.

The particle at x=0, t=0 is moving up from its mean position, & the wave travels towards the positive x-axis so the equation will be:

y = 3sin(2πt – 2πx).