A railway engine whistling at a constant frequency moves with a constant speed. It goes past a stationary observer standing beside the  railway track. The frequency $(n)$ of the sound heard by the observer is plotted against time $(t).$ Which of the following best represents the resulting curve?

Two vibrating tuning forks produce progressive waves given by $Y_1 = 4\, sin\, 500\pi \,t$ and $Y_2 = 2\, sin\, 506 \pi \,t$. Number of beats produced per minute is

A man fires a bullet standing between two cliffs. First echo is heard after $3\, seconds$ and second echo is heard after $5\, seconds$. If the velocity of sound is $330\,m/s$, then the distance between the cliffs is .... $m$

Fundamental frequency of a sonometer wire is $n$. If the length and diameter of the wire are doubled keeping the tension same, then the new fundamental frequency is

Figure shows a sinusoidal wave at a given instant Which points are in same phase ?

Two identical flutes produce fundamental notes of frequency $300\,Hz$ at $27\,^oC$. If the temperature of air in one flute is increased to $31\,^oC$, the number of the beats heard per second will be