Two trains move towards each other with the same speed. The speed of sound is 340 m/s. If the height of the tone of the whistle of one of them heard on the other changes times, then the speed of each train should be:

A wave enters to water from air. In air frequency, wavelength, intensity and velocity are n₁, λ₁, l₁ and v₁ respectively. In water the corresponding quantities are n₂, λ₂, l₁and v₂ respectively, then:

An observer moves towards a stationary source of sound with a speed th of the speed of sound. The wavelength and frequency of the source emitted are λ and ƒ respectively. The apparent frequency and wavelength recorded by the observer are respectively:

Each of the two strings of length 51.6 cm and 49.1 cm are tensioned separately by 20 N force. Mass per unit length of both the strings is same adn equal to 1 gm^-1. When both the strings vibrate simultaneously the number of beats will be:

If the amplitude of sound is doubled and the frequency reduced to one-fourth, the intensity of sound at the same point will:

The frequency of sinusoidal wave, 0.40 cos (2000t + 0.80) would be:

The driver of a car travelling with speed 30 ms-1 towards a hill sounds a horn of frequency 600 Hz. If the velocity of sound in air is 330 ms^-1, the frequency of reflected sound as heard by driver is:

A pointer source emits sound equally in all directions in a non-absorbing medium. Two points P and Q are at distance of 2m and 3m respectively from the source. The ratio of the intensities of the waves at P and Q is:

The transverse wave represented by the equation    will have :

The speed of a wave in a medium is 760 m/s. If 3600 waves are passing through a point in the medium in 2 min, then their wavelength is: