Question

What is the expression for wave speed in the given equation: y = Asin(kx-wt + π)?

(a) dy/dt

(b) w/k

(c) 2πw/k

(d) 2πk/w

The question was posed to me during an online exam.

I would like to ask this question from Speed of a Travelling Wave in division Waves of Physics – Class 11

Answer 1

The correct answer is (b) w/k

Best explanation: The distance moved by a particular value of displacement per unit time is called wave speed.                                                                                                                                                                           Basically, we have to study the motion of a fixed phase along the direction of wave propagation.                            So, kx – wt = constant.                                                                                                                                                         On differentiating we get: kdx – wdt = 0

 dx/dt = w/k, which is the wave speed.