A listener is stationary with respect to a source of sound. A wind begins blowing along the line connecting the source and the observer. Which of the following quantities remain unchanged?

Step-by-step solution

Let v be the velocity of sound in still air, v_w be the velocity of wind, and f₀ be the frequency of the source. Since the source is stationary, the effective velocity of sound relative to the ground becomes v' = v v_w . The wavelength of the sound waves is given by ' = v' f₀ = v v_w f₀ . Thus, the wavelength changes. The listener is also stationary, so the speed of sound relative to the listener is v' . The frequency observed by the listener is f' = v' ' = v v_w v v_w f₀ = f₀ . Thus, the frequency remains unchange