Explain what is meant by a longitudinal wave, with reference to the direction in which energy propagates.
A car horn produces sound of frequency $800\,\text{Hz}$. A microphone and a cathode-ray oscilloscope (c.r.o.) are used to study the sound wave. The waveform shown on the c.r.o. screen appears in Fig. $4.1$. Find the time-base setting, in $\text{s cm}^{-1}$, of the c.r.o.
The sound intensity $I$ at a distance $r$ from the car horn in (b) is described by the expression $I = \frac{k}{r^2}$, where $k$ is a constant. Fig. $4.2$ shows the car in (b) on a road.
The sound wave at point O has amplitude $A_X$ when the car is at X and amplitude $A_Y$ when the car is at Y. Calculate the ratio $\dfrac{A_Y}{A_X}$.
When the car is stationary at X, the frequency of the horn sound detected by the observer is $800\,\text{Hz}$. As the car moves from X to Y, the maximum change in detected frequency is $16\,\text{Hz}$. The speed of sound in air is $330\,\text{m s}^{-1}$. Determine, to two significant figures, the minimum wavelength of the sound detected by the observer.
When the car is stationary at X, the frequency of the horn sound detected by the observer is $800\,\text{Hz}$. As the car moves from X to Y, the maximum change in detected frequency is $16\,\text{Hz}$. The speed of sound in air is $330\,\text{m s}^{-1}$. Determine, to two significant figures, the maximum speed of the car.