The length of the string of a musical instrument is 90cm and has a fundamental frequency of 120Hz. Where should it be pressed to produce fundamental frequency of 180Hz ?

Y and Z are two partially reflecting glass sheets, a distance $$l$$​ apart in air. White light falls normally on Y. The light emerging from Z is analysed by a spectrometer. A dark band is observed in the spectrometer at a wavelength. The distance $$l$$​ must be equal to:

A tuning fork, vibrating with a frequency of 90 Hz. is moving towards an observer with a with a speed of 0.1 times the speed of sound. The frequency of the note heard by the observer would be:

Superposition of two waves trains of same amplitudes and nearly same frequencies, moving in the same direction, results in the formation of beats. The maximum loudness heard at the waxing is n times the loudness of each of the component wave trains. The value of n is:

The Poynting vector of electromagnetic waves has the same dimensions as that of:

Ultrasonic waves, propagating through a medium, can be detected by:

For a non-relativistic particle, the ratio of phase velocity to group velocity of de Broglie waves is:

When light is incident along the normal and passes from air to water, then the direction of light will _____________.