Question

Two second waves of equal intensity I produce beats. The maximum intensity of sound produced in beats will be

Solution

Correct option is

4I

 

When two waves of amplitudes a1 and a2 superpose to produce beats, the resultant amplitude of the maxima of intensity is 

                                

Now, intensity ∝ (amplitude)2. Since the two waves have the same intensity, their amplitudes are equal, i.e., a1 = a2 = a. Thus A = 2a. Therefore A2 = 4a2 or Imax = 4I.

SIMILAR QUESTIONS

Q1

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

Q2

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

Q3

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?

Q4

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

Q5

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  

Q6

 

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

Q7

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

Q8

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

Q9

A tube closed at one end containing air, produces, when excited, the fundamental note of frequency 512 Hz. If the tube is open at both ends, the fundamental frequency that can be excited in (in Hz)

Q10

Two waves of wavelength 2 m and 2.02 m moving with the same speed superpose to produce 2 beats per second. The speed of each wave is