Question:
Give an application use of ultrasonics.
Answer:
Ultrasonic sounds are used in medical field for diagnosis and treatment of internal illness of human body. e.g. kidney or gall bladder stones can be detected by ultrasound. Using ultrasound shock, such stone can be broken into small grains which later on get flushed out with urine.
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 3.
Explain the working and application of a sonar.
Q 4.
What is reverberation?
Q 5.
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 6.
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 7.
How are the wavelength and frequency of a sound wave related to its speed ?
Q 8.
How can you show that sound waves are longitudinal waves ?
Q 9.
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 10.
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 11.
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 12.
How are compressions and rarefactions produced near a source of sound ?
Q 13.
What is a longitudinal wave?
Q 14.
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 15.
How is sound propagated through a material medium ? What is wave motion ?
Q 16.
What are wavelength, frequency, time period and amplitude of a sound wave?
Q 17.
Why do we use upholstered seats in theatres and halls ?
Q 18.
Can sound wave travel in vacuum?
Q 19.
What type of waves can travel in vacuum? Give example(s).
Q 20.
What is infrasonic? Give an example.
Q 21.
Demonstrate an activity to show that sound requires a medium to travel.
Q 22.
The sonic boom of an aircraft has a time period of 0 00005 s.Calculate the frequency of the sound produced.
Q 23.
Why are sound waves called mechanical waves ?
Q 24.
Distinguish between loudness and intensity of sound.
Q 25.
How is ultrasound used for cleaning ?
Q 26.
What propagates along with the waves ?
Q 27.
Fill in the blanks :
Number of oscillations completed by the oscillator in one second is known as ___________.
Q 28.
Fill in the blanks :
Audible sound range is _________ to _____________.
Q 29.
Fill in the blanks :
The product of wavelength of wave and its frequency gives _____________.
Q 30.
What is speed of sound in air?
Q 31.
Among solids, liquids and gases sound travels faster in which medium?
Q 32.
How are the wavelength and frequency of a sound wave related to its speed?
Q 33.
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 34.
Write differences between Transverse waves and Longitudinal waves.
Q 36.
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 37.
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 38.
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 39.
Radio Ceylon broadcasts at 25 m.What is the frequency of the station ?
Q 40.
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 41.
Describe with the help of a diagram,how compressions and rarefactions are produced in air near a source of sound.
Q 42.
Cite an experiment to show that sound needs a material medium for its propagation.
Q 43.
Explain how defects in a metal block can be detected using ultrasound.
Q 44.
Explain how the human ear works.
Q 45.
Can sound waves travel through vacuum ?
Q 46.
What is audible range ?
Q 47.
What is acoustical transite ?
Q 48.
Can you produce sound without utilizing energy ?
Q 49.
By how much does the speed of sound increase with rise of temperature ?
Q 50.
How can you make a building sound proof ?
