A cylindrical tube $(L = 120\, cm.)$ is resonant with a tuning fork of frequency $330\, Hz$. If it is filling by water then to get resonance again, minimum length of water column is  ...... $cm$  $(v_{air} = 330\, m/s)$

The diagram shows snapshot of a wave at time $t = 0$. The particle at $x = x_1$ is moving upward at that instant. Direction of propagation of wave is

A wave travelling in the $-ve\,\,z-$ direction having displacement along $x-$ direction as $1\,m,$ wavelength $\pi\, m$ and frequency at $\frac {1}{\pi }\,H_Z$ is represented by

When two waves of almost equal frequencies $v_1$ and $v_2$ reach at a point simultaneously, the time interval between successive maxima is

An engine is moving towards a wall with a velocity $50\, ms^{-1}$ emits a note of $1.2\, kHz$. The speed of sound in air is $350\, ms^{-1}$. The frequency of the note after reflection from the wall as heard by the driver of the engine is ..... $kHz$

An engine approaches a hill with a constant speed. When it is at a distance of $0.9 km$ it blows a whistle, whose echo is heard by the driver after $5$ sec. If speed of sound in air is $330 m/s$, the speed of engine is .... $m/s$