Question:
What are infrasonics ?
Answer:
Sounds with frequencies less than 20 Hz are called infrasonics.
Sound
Q 1.
What are the factors speed of sound wave depends upon?
Q 2.
Fill in the blanks :
v = ? × ?
Q 3.
Explain how sound is produced by your school bell ?
Q 4.
What propagates along with the waves ?
Q 5.
Why do we use upholstered seats in theatres and halls ?
Q 6.
Explain how the human ear works.
Q 7.
How does sound travel in gases and liquids as longitudinal or as transverse waves?
Q 8.
Radio Ceylon broadcasts at 25 m.What is the frequency of the station ?
Q 9.
Fill in the blanks :
Loudness of sound is measured in ___________.
Q 10.
What is the audible range?
Q 11.
What is a sonic boom ?
Q 12.
What is acoustical transite ?
Q 13.
What is a wave number?
Q 14.
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 15.
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 16.
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 17.
Obtain a relation between speed,frequency and wavelength of a wave.
Q 18.
Try to imagine what you would feel, what sort of person you would be,had you been born totally deaf.
Q 19.
Fill in the blanks :
Waves transport _________ not matter.
Q 20.
Fill in the blanks :
Sound having frequency less than 20Hz is known as ___________.
Q 21.
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 22.
Distinguish between loudness and intensity of sound.
Q 23.
is sound wave called a longitudinal wave ?
Q 24.
What is reverberation ? How can it be reduced ?
Q 25.
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 26.
Distinguish between music and noise.
Q 27.
Why sound waves are called mechanical waves?
Q 28.
Can sound wave travel in vacuum?
Q 29.
What type of waves can travel in vacuum? Give example(s).
Q 30.
Give examples of organisms which can hear infrasonic?
Q 31.
A sound wave has a frequency of 2
kHz and wavelengtl 35 cm.How long will it take to travel 1.5 km ?
Q 32.
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 33.
What are wavelength,frequency,time period and amplitude of a sound wave ?
Q 34.
Calculate the wavelength of a sound wave whose frequency is 220 Hz and speed is 440 m/s in a given medium.
Q 35.
What is the audible range of the average human ear ?
Q 36.
Describe with the help of a diagram,how compressions and rarefactions are produced in air near a source of sound.
Q 37.
Explain how defects in a metal block can be detected using ultrasound.
Q 38.
What is persistence of hearing ?
Q 39.
We see flash earlier than the thunder.Discuss.
Q 40.
Deaf people can be made to dance to music.Explain how ?
Q 41.
What travels faster : a rifle bullet or the sound of the shot fired from it ?
Q 42.
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 43.
Fill in the blanks :
In a _____________ wave the particles of the medium oscillate in the direction in which the wave travels.
Q 44.
Fill in the blanks :
Sound, compressional waves in springs are examples of _____________.
Q 45.
Fill in the blanks :
Audible sound range is _________ to _____________.
Q 46.
Fill in the blanks :
The product of wavelength of wave and its frequency gives _____________.
Q 47.
Fill in the blanks :
Existence of sound waves in an auditorium due to multiple reflections suffered by the walls and ceiling is called ____________.
Q 48.
Give examples of longitudinal waves.
Q 49.
What are wavefronts?
Q 50.
Suppose you and your friend are on the Moon. Will you be able to hear any sound produced by your friend?
