The phase difference between two points separated by $0.8 m$ in a wave of frequency $120 Hz$ is ${90^o}$. Then the velocity of wave will be ............ $\mathrm{m/s}$

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

A train standing at the outer signal of a railway station blows a whistle of frequency $400\, Hz$ in still air. What is the frequency of the whistle for a platform observer when the train recedes from the platform with a speed of $10\, m/s$ ...... $Hz$ . (Speed of sound $= 340\, m/s$)

A sufficiently long closed organ pipe has a small hole at its bottom. Initially, the pipe is empty. Water is poured into the pipe at a constant rate. The fundamental frequency of the air column in the pipe

A train approaching a railway plateform with a speed of  $20\,\,m\,s^{-1}$ starts blowing the whistle speed of sound in air is $340\,\,ms^{-1}.$ If frequency of the emitted sound from the whistle is  $640\,\,Hz,$  the frequency of sound as heard by person standing on the platform is .... $Hz$

A transverse wave is passing through a stretched string with a speed of $20\  m/s$ . The tension in the string is $20\ N$ . At a certain point $P$ on the string, it is observed that energy is being transferred at a rate of $40\ mW$ at a given instant. Find the speed of point $P$