A string fixed at one end is vibrating in its second overtone. The length of the string is $10\  cm$ and maximum amplitude of vibration of particles of the string is $2\ mm$ . Then the amplitude of the particle at $9\ cm$ from the open end 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 uniform string suspended vertically. A transverse pulse is created at the top most of the string. Then

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 point source emits sound equally in all directions in a non-absorbing medium. Two points $P$ and $Q$ are at a distance of $9\  meters$ and $25\  meters$ respectively from the source. The ratio of the amplitudes of the waves at $P$ and $Q$ is