Question:
Describe with the help of a diagram,how compressions and rarefactions are produced in air near a source of sound.
Answer:
Refer to Art. 6.6,Page 326.
Sound
Q 1.
What are the factors speed of sound wave depends upon?
Q 2.
What is a wave number?
Q 3.
What are ultrasonics?
Q 4.
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 5.
How is sound propagated through a material medium ? What is wave motion ?
Q 6.
How are compressions and rarefactions produced near a source of sound ?
Q 7.
What type of waves can travel in vacuum? Give example(s).
Q 8.
Fill in the blanks :
The product of wavelength of wave and its frequency gives _____________.
Q 9.
Fill in the blanks :
v = ? × ?
Q 10.
What is infrasonic? Give an example.
Q 12.
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 13.
How does sound travel in gases and liquids as longitudinal or as transverse waves?
Q 14.
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 15.
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 16.
Explain how sound is produced by your school bell ?
Q 17.
What is audible range ?
Q 18.
Why do we use upholstered seats in theatres and halls ?
Q 19.
Fill in the blanks :
Waves transport _________ not matter.
Q 20.
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 21.
How are the wavelength and frequency of a sound wave related to its speed?
Q 22.
What type of wave is represented by density- distance graph?
Q 23.
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 24.
What propagates along with the waves ?
Q 25.
Deaf people can be made to dance to music.Explain how ?
Q 26.
What is speed of sound in air?
Q 27.
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 28.
Give an application use of ultrasonics.
Q 29.
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 30.
Fill in the blanks :
Sound, compressional waves in springs are examples of _____________.
Q 31.
What is a mechanical wave?
Q 32.
What are wavelength, frequency, time period and amplitude of a sound wave?
Q 33.
What is reverberation?
Q 34.
Guess which sound has a higher pitch: guitar or car horn?
Q 35.
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 36.
How are the wavelength and frequency of a sound wave related to its speed ?
Q 37.
Explain the working and application of a sonar.
Q 38.
Obtain a relation between speed,frequency and wavelength of a wave.
Q 39.
What is sonic boom and when is it heard ?
Q 40.
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 41.
What is Sound? Why it is important for us?
Q 42.
Calculate the wavelength of a sound wave whose frequency is 220 Hz and speed is
440 m/s in a given medium.
Q 43.
Distinguish between loudness and intensity of sound.
Q 44.
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 45.
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 46.
How does the sound produced by a vibrating object in a medium reach your ear ?
Q 47.
What is the audible range of the average human ear ?
Q 48.
A stone is dropped from the top of a tower 500 m high into a pond of water at the base of the tower.When is the splash heard at the top ? Given,g = 10
and speed of sound = 340 m/s.
Q 49.
How is ultrasound used for cleaning ?
Q 50.
How can you show that sound waves are longitudinal waves ?
