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.
What are the factors speed of sound wave depends upon?
Q 2.
What is audible range ?
Q 3.
What are ultrasonics?
Q 4.
How is sound propagated through a material medium ? What is wave motion ?
Q 5.
What is speed of sound in air?
Q 6.
What is a wave number?
Q 7.
What is infrasonic? Give an example.
Q 8.
How are compressions and rarefactions produced near a source of sound ?
Q 9.
How does sound travel in gases and liquids as longitudinal or as transverse waves?
Q 10.
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 11.
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 12.
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 13.
How are the wavelength and frequency of a sound wave related to its speed ?
Q 14.
What propagates along with the waves ?
Q 16.
Calculate the wavelength of a sound wave whose frequency is 220 Hz and speed is
440 m/s in a given medium.
Q 17.
What are wavelength, frequency, time period and amplitude of a sound wave?
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.
Fill in the blanks :
v = ? × ?
Q 20.
If 20 waves are produced per second, what is the frequency in hertz?
Q 21.
Give an application use of ultrasonics.
Q 22.
Which wave characteristics determine the
(a) Loudness (b) pitch of sound?
Draw two different waveforms and mark these characteristics on it.
Q 23.
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 24.
Explain how sound is produced by your school bell ?
Q 25.
By how much does the speed of sound increase with rise of temperature ?
Q 26.
Why do we use upholstered seats in theatres and halls ?
Q 27.
Fill in the blanks :
Sound, compressional waves in springs are examples of _____________.
Q 28.
What is a mechanical wave?
Q 29.
What type of wave is represented by density- distance graph?
Q 30.
A ship sends out ultrasound that returns from the seabed and is detected after 3.42 s.If the speed of the ultrasound through sea water is 1531 m/s,what is the distance of the seabed from the ship ?
Q 31.
Why are sound waves called mechanical waves ?
Q 32.
Obtain a relation between speed,frequency and wavelength of a wave.
Q 33.
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 34.
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 35.
Fill in the blanks :
Ripples waves on water surface are example of ____________.
Q 36.
Fill in the blanks :
In a _____________ wave the particles of the medium oscillate in the direction in which the wave travels.
Q 37.
Fill in the blanks :
Full form of SONAR is __________________________.
Q 38.
Three persons, A, B and C are made to hear a sound travelling through different mediums as given below:
| Persons | Medium |
| A | Iron Rod |
| B | Air |
| C | Water |
Who will hear the sound first? Why?
Q 39.
How does the sound produced by a vibrating object in a medium reach your ear?
Q 40.
Fill in the blanks :
If a body repeats its back and forth, to and fro or up and down motion along a certain path, about a fixed point, in a certain time interval then the motion of such objects is said to be _____________.
Q 41.
Fill in the blanks :
If the time interval between original sound and reflected sound is more than 1/10 second then original sound and reflected sound can be heard clearly. This reflected sound is known as _______.
Q 42.
Why sound waves are called mechanical waves?
Q 43.
Why transverse wave does not travel through air or gases?
Q 44.
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 45.
The frequency of a source of sound is 100 Hz.How many times does it vibrate in a minute ?
Q 46.
What is sonic boom and when is it heard ?
Q 47.
What is an echo ? How is it formed ?
Q 48.
Discuss the structure of human ear from auditory aspect only.
Q 49.
Sounds we hear inform us of the state of world around us,especially of that part of it which our other senses,such as touch and sight,cannot reach.Illustrate this with appropriate examples.
Q 50.
Today our life is richer and fuller of music than it was yesterday,and much of this is due to progress in engineering.What will happen to human feelings when the sea of knowledge spreads further ?
