Question:
Can sound wave travel in vacuum?
Answer:
No Sound is a mechanical wave, it requires a medium to travel.
Sound
Q 1.
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 2.
How is sound propagated through a material medium ? What is wave motion ?
Q 3.
How does sound travel in gases and liquids as longitudinal or as transverse waves?
Q 4.
How are the wavelength and frequency of a sound wave related to its speed ?
Q 5.
Hearing may be damaged by excessive noise.So our ears sometimes need protection from continuous loud sound. Hearing damage depends on the sound intensity level (decibel level)and the exposure time,and the exact combinations vary for different people.Normally,at 90 dB,it takes 8 hours or less for the damage to receptor nerves to occur.Further,it is found that if the sound level is increased by 5 dB,the safe exposure limit is cut to half.
(a) How long will it take for a sound of a very loud lawn mower (or a motorcycle) of 95dB to damage the hearing ?
(b) What is the nonstop exposure time for a 105 dB sound to damage the ear ?
(c) What should be done to protect the society from the danger of losing the divine gift of hearing power ?
Q 6.
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 7.
How are compressions and rarefactions produced near a source of sound ?
Q 8.
What is audible range ?
Q 9.
By how much does the speed of sound increase with rise of temperature ?
Q 10.
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 11.
How are the wavelength and frequency of a sound wave related to its speed?
Q 12.
Calculate the wavelength of a sound wave whose frequency is 220 Hz and speed is
440 m/s in a given medium.
Q 13.
A person is listening to a tone of 500 Hz sitting at a distance of 450 m from the source of the sound. What is the time interval between successive compressions from the source?
Q 14.
Why do we use upholstered seats in theatres and halls ?
Q 15.
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 16.
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 17.
Why are sound waves called mechanical waves ?
Q 18.
Deaf people can be made to dance to music.Explain how ?
Q 19.
Fill in the blanks :
Number of oscillations completed by the oscillator in one second is known as ___________.
Q 20.
Fill in the blanks :
Sound, compressional waves in springs are examples of _____________.
Q 21.
Fill in the blanks :
v = ? × ?
Q 22.
What is speed of sound in air?
Q 23.
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 24.
Write differences between Transverse waves and Longitudinal waves.
Q 25.
What type of wave is represented by density- distance graph?
Q 26.
Demonstrate an activity to show that sound requires a medium to travel.
Q 27.
A boat anchor is rocked by waves whose consecutive crests are 100 m apart.If the wave speed of the moving crests is 20 m/s,calculate the frequency at which the boat rocks.
Q 28.
A longitudinal wave is produced on a slinky.The frequency of the wave is 25 Hz and it travels at a speed of 20 cm/s. Find the separation between consecutive positions of maximum compressions.
Q 29.
A bat emits ultrasonic sound of frequency 100 kHz in air.If this sound meets a water surface,what is the wavelength of (a) the reflected sound wave (b) the transmitted sound wave ?
Given speed of sound in air = 340 m/s and in water = 1486 m/s.
Q 30.
A wave of wavelength 0-60 cm is produced in air and it travels at a speed of 300 m/s.Will it be audible ?
Q 31.
A person clapped his hands near a cliff and heard the echo after 5 s.What is the distance of the cliff from the person if the speed of the sound,v is taken as 346 m/s ?
Q 32.
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 33.
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 34.
Guess which has a higher pitch : a guitar or a car horn ?
Q 35.
What is the audible range of the average human ear ?
Q 36.
What is sound and how is it produced ?
Q 37.
Cite an experiment to show that sound needs a material medium for its propagation.
Q 38.
Explain how the human ear works.
Q 39.
What is a sonic boom ?
Q 41.
Discuss the role of medium in the propagation of sound.
Q 42.
Distinguish between music and noise.
Q 43.
Describe an experiment to show that sound waves can be reflected.What are the laws of reflection of sound waves.
Q 44.
What is the range of frequencies of audio waves,infrasonics and ultrasonics ?
Q 45.
What are the characteristics of a sound ? Discuss each one of them briefly.
Q 46.
What is SONAR ? How is it used to detect an underwater object and measure its distance
Q 47.
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 48.
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 49.
Fill in the blanks :
Sound travels as successive ____________ and _____________ in the medium.
Q 50.
Fill in the blanks :
In a _____________ wave the particles of the medium oscillate in the direction in which the wave travels.
