Question:
What are multiple echoes ? Discuss any two of their important practical applications.
Answer:
Refer to Art.6.22,Page 347.
Sound
Q 1.
What are the factors speed of sound wave depends upon?
Q 2.
Fill in the blanks :
v = ? × ?
Q 3.
Why do we use upholstered seats in theatres and halls ?
Q 4.
What propagates along with the waves ?
Q 5.
Explain how sound is produced by your school bell ?
Q 6.
What is a wave number?
Q 7.
Calculate the wavelength of a sound wave having a frequency 300 Hz and speed 330 m/s.
Q 8.
Explain how the human ear works.
Q 9.
How does sound travel in gases and liquids as longitudinal or as transverse waves?
Q 10.
Obtain a relation between speed,frequency and wavelength of a wave.
Q 11.
How is sound propagated through a material medium ? What is wave motion ?
Q 12.
What are ultrasonics?
Q 13.
Radio Ceylon broadcasts at 25 m.What is the frequency of the station ?
Q 14.
Try to imagine what you would feel, what sort of person you would be,had you been born totally deaf.
Q 15.
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 16.
What is reverberation ? How can it be reduced ?
Q 17.
Can sound wave travel in vacuum?
Q 18.
What is the audible range?
Q 19.
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 20.
Calculate the wavelength of a sound wave whose frequency is 220 Hz and speed is 440 m/s in a given medium.
Q 21.
Distinguish between loudness and intensity of sound.
Q 22.
Explain how defects in a metal block can be detected using ultrasound.
Q 23.
Draw a curve showing density or pressure variations with respect to distance for a disturbance produced by sound.Mark the position of compression and rarefaction on this curve.Also define wavelengths and time period using this curve.
Q 24.
Write the name of the wave which propagates in terms of compressions and rarefactions.
Q 25.
Can sound waves travel through vacuum ?
Q 26.
What are infrasonics ?
Q 27.
Can you produce sound without utilizing energy ?
Q 28.
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 29.
Discuss the role of medium in the propagation of sound.
Q 30.
What travels faster : a rifle bullet or the sound of the shot fired from it ?
Q 31.
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 32.
Fill in the blanks :
In a _____________ wave the particles of the medium oscillate in the direction in which the wave travels.
Q 33.
Fill in the blanks :
Audible sound range is _________ to _____________.
Q 34.
Fill in the blanks :
Loudness of sound is measured in ___________.
Q 35.
Why sound waves are called mechanical waves?
Q 36.
What type of waves can travel in vacuum? Give example(s).
Q 37.
What are wavelength, frequency, time period and amplitude of a sound wave?
Q 38.
What type of wave is represented by density- distance graph?
Q 39.
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 40.
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 41.
Describe with the help of a diagram,how compressions and rarefactions are produced in air near a source of sound.
Q 42.
Does sound follow the same laws of reflection as light does ? Explain.
Q 43.
Explain how bats use ultrasound to catch a prey.
Q 44.
Explain the working and application of a sonar.
Q 45.
What is acoustical transite ?
Q 46.
What is persistence of hearing ?
Q 47.
Distinguish between music and noise.
Q 48.
Describe an experiment to show that sound waves can be reflected.What are the laws of reflection of sound waves.
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 ?
