A cylindrical tube, open at both ends, has a fundamental frequency V in air. The tube is dipped vertically in water so that half of it is inside water. The fundamental frequency of the air column now is


Correct option is



The frequency of the fundamental mode in an open pipe is given by


And in a closed pipe it is  


Where v is the speed of sound and L is the length of the pipe.

When the tube is dipped in water, L becomes L/2 and V’ becomes


From (i) and (ii) we get V’’ = V.



Two identical flutes produce fundamental notes of frequency 300 Hz at 27oC. If the temperature of the air in one flute is increased to 31oC, the number of beats heard per second will be


The wavelength of light of a particular wavelength received from a galaxy is measured on earth and is found to be 5% more that its wavelength. It follows that the galaxy is


Radio waves of frequency 600 MHz are sent by a radar towards an enemy aircraft. The frequency of the radio waves reflected from the aircraft as measured at the radar station is found to increase by 6 kHz. It follows that the aircraft is


Three waves of equal frequency having amplitude 10 μm, 4 μm and 7μ arrive at a given point with a successive phase difference of π/2. The amplitude of the resulting wave in μ m is given by


Two wires of the same material and radii r and 2r are welded together end to end. The combination is used as a sonometer wire and kept under tension T. The welded point is mid-way between the two bridges. When stationary waves are set up in the composite wire, the joint is a node. Then the ratio of the number of loops formed in the thinner to thicker wire is


A uniform rope of length 12m and mass 6 kg hangs vertically from a rigid support. A block of mass 2 kg is attached to the free end of the rope. A transverse pulse of wavelength 0.06 m is produced in the lower end of the rope. What is the wavelength of the pulse when it reached the top of the rope?


A tuning fork and a sonometer wire sounded together produce 4 beats per second when the length of the wire is 95 cm or 100 cm. the frequency of the turning fork is


An object producing a sound of frequency 400 Hz approaches a stationary person with a speed of 200 ms–1. The speed of sound is 300 ms–1. As the object flies past him, the person will note a change in frequency of  



The frequency of the sound of a car horn as received by an observer towards whom the car is moving differs from the frequency of the horn by 2.5%. If the speed of sound in air is

320 ms–1, the speed of the car is


The intensity of a sound wave falls by 10% in travelling a distance of 1 metre in a medium. If the initial intensity of the sound wave was 100 decibels, its value after it passes through 3 metres thickness of the medium will be