A car $P$ approaching a crossing at a speed of $10\, m/s$ sounds a horn of frequency $700\, Hz$ when $40\, m$ in front of the crossing. Speed of sound in air is $340\, m/s$. Another car $Q$ is at rest on a road which is perpendicular to the road on which car $P$ is reaching the crossing (see figure). The driver of car $Q$ hears the sound of the horn of car $P$ when he is $30\, m$ in front of the crossing. The apparent frequency heard by the driver of car $Q$ is   .... $Hz$

A transverse wave is described by the equation $y = {y_0}\,\sin \,2\pi \left( {ft - \frac{x}{\lambda }} \right)$ . The maximum particle velocity is equal to four times the wave velocity if

In a resonance tube experiment, the first resonance is obtained for $10\, cm$ of air column and the second for $32\, cm$. The end correction for this apparatus is ....$cm$

Two waves represented by, $y_1 = 10\,sin\, 200\pi t$ , ${y_2} = 20\,\sin \,\left( {2000\pi t + \frac{\pi }{2}} \right)$ are superimposed at any point at a particular instant. The amplitude of the resultant wave is

The length of open organ pipe is $L$ and fundamental frequency is $f$. Now it is immersed into water upto half of its length now the frequency of organ pipe will be

Four sources of sound each of sound level $10\,dB$ are sounded together, there sultant intensity level will be ... $dB$