Question:
The sound of distant horses can be heard by applying the ear to the ground whereas it is inaudible if the ear is held a little distance above the ground.Explain.
Answer:
We know that loudness is directly proportional to the density of the medium.The density of ground is much higher than that of air.Thus,the sound of distant horses,when conveyed through ground,is louder than when through air.Therefore,by applying ear to the ground,we can hear this sound.But when the ear is a little distance above the ground,the sound travels through air and is hardly audible.
Sound
Q 1.
How is sound propagated through a material medium ? What is wave motion ?
Q 2.
What is audible range ?
Q 3.
What is infrasonic? Give an example.
Q 4.
How are compressions and rarefactions produced near a source of sound ?
Q 5.
A hospital uses an ultrasonic scanner to locate tumors in a tissue. What is the wavelength of sound in a tissue is which the speed of sound is 1.7 km/s. The operating frequency of the scanner is 4.2 MHz. (1MHz = 10
6 Hz).
Q 6.
What are ultrasonics?
Q 7.
What are the factors speed of sound wave depends upon?
Q 8.
How are the wavelength and frequency of a sound wave related to its speed ?
Q 9.
By how much does the speed of sound increase with rise of temperature ?
Q 10.
Obtain a relation between speed,frequency and wavelength of a wave.
Q 11.
Fill in the blanks :
Sound, compressional waves in springs are examples of _____________.
Q 12.
How does sound travel in gases and liquids as longitudinal or as transverse waves?
Q 13.
What is speed of sound in air?
Q 14.
What is a wave number?
Q 15.
Calculate the wavelength of a sound wave whose frequency is 220 Hz and speed is
440 m/s in a given medium.
Q 16.
An observer standing at the sea coast observes 54 waves reaching the coast per minute.If the wavelength of a wave is 10 m,find the wave velocity.
Q 17.
A man standing at 51 m from a wall fires a gun.Calculate the time after which an echo is heard.The speed of sound is 340 m/s.
Q 18.
A sound wave travels at a speed of 339 ms
–1. If its wavelength is 1.5 cm, what is the frequency of the wave?
Q 19.
Explain how sound is produced by your school bell ?
Q 20.
What propagates along with the waves ?
Q 21.
Why do we use upholstered seats in theatres and halls ?
Q 22.
Fill in the blanks :
v = ? × ?
Q 23.
Why transverse wave does not travel through air or gases?
Q 24.
Give an application use of ultrasonics.
Q 25.
A person standing between two vertical cliffs and 680 m away from the nearest cliff,shouted.He heard the first echo after 4 s and the second echo 3 s later.Calculate (a) the speed of sound in air and (b) distance between the two cliffs.
Q 26.
sonar emits pulses on the surface of water which are detected after reflection from its bottom at a depth 1531 m.If the time interval between the emission and detection of the pulse is 2 s,find the speed of : sound in water.
Q 27.
Why are sound waves called mechanical waves ?
Q 28.
Explain the working and application of a sonar.
Q 30.
The sound of distant horses can be heard by applying the ear to the ground whereas it is inaudible if the ear is held a little distance above the ground.Explain.
Q 31.
Try to imagine what you would feel, what sort of person you would be,had you been born totally deaf.
Q 32.
Fill in the blanks :
A ________ (pulse/wave) is a form of disturbance which travels through a medium as a result of repetitive oscillations of the particles of the medium.
Q 33.
Fill in the blanks :
In a __________ wave the particles of the medium oscillate in a direction perpendicular to the direction in which the wave propagates.
Q 34.
Fill in the blanks :
Full form of SONAR is __________________________.
Q 35.
What is a mechanical wave?
Q 36.
How does the sound produced by a vibrating object in a medium reach your ear?
Q 37.
What are wavelength, frequency, time period and amplitude of a sound wave?
Q 38.
If 20 waves are produced per second, what is the frequency in hertz?
Q 39.
What type of wave is represented by density- distance graph?
Q 40.
An engine is approaching a hill at constant speed.When it is at a distance of 0.9 km,it blows a whisde,whose echo is heard by the driver after 5 s.If the speed of sound is 340 m/s,calculate the speed of the engine.
Q 41.
How does the sound produced by a vibrating object in a medium reach your ear ?
Q 42.
What is the audible range of the average human ear ?
Q 43.
What is persistence of hearing ?
Q 44.
What is the difference between an echo and a reverberation ?
Q 45.
Discuss the structure of human ear from auditory aspect only.
Q 46.
On what factors does the speed of sound in a material depend ?
Q 47.
Fill in the blanks :
Number of oscillations completed by the oscillator in one second is known as ___________.
Q 48.
Fill in the blanks :
The product of wavelength of wave and its frequency gives _____________.
Q 49.
Why sound waves are called mechanical waves?
Q 50.
What type of waves can travel in vacuum? Give example(s).
