Three waves of equal frequency having amplitudes $10\,\mu m$, $4\,\mu m$, $7\,\mu m$ arrive at a given point with successive phase difference of $\pi /2$, the amplitude the resulting wave in $\mu m$ is given by

A car sounding its horn at $480\,Hz$ moves towards a high wall at a speed of $20\,m/s$. If the speed of sound is $340\,m/s,$ the frequency of the reflected sound heard by the passenger sitting in the car will be the nearest to ..... $Hz$

A string of mass $2.5\ kg$ is under a tension of $200\ N$ . The length of the stretched string is $20.0\ m$ . If the transverse jerk is struck at one end of the string, the disturbance will reach the other end in .... $\sec$

If $L_1$ and $L_2$ are the lengths of the first and second resonating air columns in a resonance tube, then the wavelength of the note produced is

The equation of displacement of two waves are given as ${y_1} = 10\,\sin \,\left( {3\pi t\, + \,\pi /3\,} \right)$ , ${y_2} = 5\,\left( {\sin \,3\pi t + \,\sqrt 3 \,\cos \,3\pi t} \right)$ , then what is the ratio of their amplitude 

A racing car moving towards a cliff sounds its horn. The driver observes that the sound reflected from the cliff has a pitch one octave higher than the actual sound of the horn. If $v$ is the velocity of sound, the velocity of the car will be