Four tuning forks of frequencies $200,201, 204$ and $206\, Hz$ are sounded together.  The beat frequency will be

Dependence of disturbances due to two waves on time is shown in the figure. The ratio of their intensities $I_1 / I_2$ will be

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 wave velocity if

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 …… $Hz$

The two waves represented by $y_1 = a\,sin(\omega\,t)$ and $y_2 = b\, cos\, (\omega\, t)$ have a phase difference of