A sound wave with frequency f 0 and wavelength λ 0 travels …

Physics Wave and Sound Mix MCQ (Single Correct)

A sound wave with frequency f 0 and wavelength λ 0 travels horizontally toward the right. It strikes and is reflected from a large, rigid, vertical plane surface, perpendicular to the direction of propagation of the wave and moving toward the left with a speed v 1 .

How many positive wave crests strike the surface in a time interval t?

At the end of this time interval, how far to the left of the surface is the wave that was reflected at the beginning of the time interval?

What is the wavelength of the reflected waves in terms of λ 0 ?

What is the frequency of the reflected waves in terms of f 0 ? (e) A listener is at rest at the left of the moving surface. How many beats per second does she detect as a result of the combined effect of the incident and reflected waves?

Text Solution

Verified by Experts

The correct answer is:

CHECK THE SOLUTION.

In a time , the wall has moved a distance vit and the wavefront that hits the wall at time has traveled a distance vt , where , and the number of wave crests in the total distance is
The reflected wave has traveled vt and the wall has moved vit, so the wall and the wavefront are separated by .
The distance found in part must contain the number of reflected waves found in part , and the ratio of the quantities is the wavelength of the reflected wave, .
The speed divided by the result of part , expressed in terms of is .
(e) .