EASY
Earn 100

Explain applications of beats.

Important Questions on Sound Waves

MEDIUM
Two vibrating strings ' A ' and ' B ' produce beats of frequency 8 Hz. The beat frequency is found to reduce to 4 Hz if the tension in the string 'A' is slightly reduced. If the original frequency of A is 320 Hz, then the frequency of B ' is
EASY
A source of sound gives 5 beats per second when sounded with another source of frequency 100 s-1. The second harmonic of the source together with a source of frequency 205 s-1 gives 5 beats per second. The frequency of the source is
EASY
Two sound waves with wavelengths 5.0 m and 5.5 m, respectively, each propagates in gas with velocity 330 m s-1. The number of beats that can be expected from them per second is
MEDIUM
The velocity of sound in a gas, in which two wavelengths 4.08 m and 4.16 m produce 40 beats in 12 s, will be
MEDIUM
The correct figure that shows, schematically, the wave pattern produced by the superposition of two waves of frequencies 9 Hz and 11 Hz, is
MEDIUM
A source of sound emitting at a frequency f is moving towards a wall with speed vb. If v is the speed of sound then the beat frequency heard by a stationary observer behind the source is
EASY
A tuning fork A of unknown frequency produces 5 beats s-1 with a fork of known frequency 340 Hz. When fork A is filed, the beat frequency decreases to 2 beats s-1. What is the frequency of fork A ?
MEDIUM
A uniform rope of length L and mass m1, hangs vertically from a rigid support. A block of mass m2 is attached to the free end of the rope. A transverse pulse of wavelength λ1 is produced at the lower end of the rope. The wavelength of the pulse when it reaches the top of the rope is λ2. The ratio λ2λ1 is:
EASY
In a guitar, two strings A and B made of same material are slightly out of tune and produce beats of frequency 6 Hz. When tension in B is slightly decreased, the beat frequency increases to 7 Hz. If the frequency of A is 530 Hz, the original frequency of B will be:
MEDIUM
A closed organ pipe and an open organ pipe of same length produce 2 beats sec-1 when they are set into vibrations together in fundamental mode. The length of open pipe is now halved and that of closed pipe is doubled. The number of beats produced will be
EASY
A set of 20 tuning forks is arranged in a series of increasing frequencies. If each fork gives 4 beats with respect to the preceding fork and the frequency of the last fork is twice the frequency of the first, then the frequency of last fork is _____ Hz.
EASY
Three sound waves of equal amplitudes have frequencies, (n  1), n, (n + 1). They superimpose to give beats. The number of beats produced per second will be
MEDIUM
An observer is riding on a bicycle and moving towards a hill at 18 km h-1. He hears a sound from a source at some distance behind him directly as well as after its reflection from the hill. If the original frequency of the sound as emitted by source is 640 Hz and velocity of the sound in air is 320 m s-1, the beat frequency between the two sounds heard by observer will be _____ Hz.
EASY
Two tuning forks have frequencies 450 Hz and 454 Hz respectively. On sounding these forks together, the time interval between two successive maximum intensities will be _______.
EASY
A tuning fork vibrates with frequency 256 Hz and gives one beat per second with the third normal mode of vibration of an open pipe. What is the length of the pipe? (speed of sound in air is 340 m s-1)
HARD
Two loudspeakers M and N are located 20 m apart and emit sound at frequencies 118 Hz and 121 Hz, respectively. A car is initially at a point P, 1800 m away from the midpoint Q of the line MN and moves towards Q constantly at 60 km h-1 along the perpendicular bisector of MN. It crosses Q and eventually reaches a point R, 1800 m away from Q. Let νt represent the beat frequency measured by a person sitting in the car at time t. Let νp, νQ and νR be the beat frequencies measured at locations P, Q and R, respectively. The speed of sound in air is 330 m s-1. Which of the following statement(s) is (are) true regarding the sound heard by the person?
EASY
An air column, closed at one end and open at the other, resonates with a tuning fork when the smallest length of the column is 50cm . The next larger length of the column resonating with the same tuning fork is:
MEDIUM
The frequency of two tuning forks A and B are 1.5% more and 2.5% less than that of the tuning fork C. When A and B are sounded together, 12 beats are produced in 1 second. The frequency of tuning fork C is
MEDIUM
A toy-car, blowing its horn, is moving with a steady speed of 5 m s-1, away from a wall. An observer, towards whom the toy car is moving, is able to hear 5 beats per second. If the velocity of sound in air is 340 m s-1 the frequency of the horn of the toy car is close to
MEDIUM
Two sitar strings, A and B playing the note 'Dha' are slightly out of tune and produce beats of frequency 5 Hz. The tension of the string B is slightly increased and the beat frequency is found to decrease by 3 Hz. If the frequency of A is 425 Hz. The original frequency of B is