A point source emits sound equally in all directions in a non-absorbing medium. Two points $P$ and $Q$are at distances of $2m$ and $3m$ respectively from the source. The ratio of the intensities of the waves at $P$ and $Q$ is

 Two cars $A$ and $B$ are moving in the same direction with speeds $36\,km/hr$ and $54\,km/hr$ respectively. Car $B$ is ahead of $A$. If $A$ sounds horn of frequency $1000\,Hz$ and the speed of sound in air is $340\,m/s$, the frequency of sound received by the driver of car $B$ is .................. $\mathrm{Hz}$

A train whistling at constant frequency is moving towards a station at a constant speed $V$. The train goes past a stationary observer on the station. The frequency $n'$ of the sound as heard by the observer is plotted as a function of time $t (Fig.)$ . Identify the expected curve

Two waves $Y_1=A_1 \sin \,(\omega t -\beta_1)$ and $Y_2 = A_2 \sin \,(\omega t -\beta_2)$ superimpose to form a resultant wave whose amplitude is

A sound absorber attenuates (decreases) the sound level by $20\, dB$. The intensity decreases by a factor of

The wave described by $y = 0.25\,\sin \,\left( {10\pi x - 2\pi t} \right)$ , where $x$ and $y$ are in $meters$ and $t$ in $seconds$ , is a wave travelling along is