Question:
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.
Answer:
We know that loudness is directly proportional to the density of the medium.The density of ground is much higher than that of air.Thus,the sound of distant horses,when conveyed through ground,is louder than when through air.Therefore,by applying ear to the ground,we can hear this sound.But when the ear is a little distance above the ground,the sound travels through air and is hardly audible.
Sound
Q 1.
Fill in the blanks :
v = ? × ?
Q 2.
What are the factors speed of sound wave depends upon?
Q 3.
Why do we use upholstered seats in theatres and halls ?
Q 4.
What propagates along with the waves ?
Q 5.
What are ultrasonics?
Q 6.
How is sound propagated through a material medium ? What is wave motion ?
Q 7.
Explain how sound is produced by your school bell ?
Q 8.
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 9.
What are wavefronts?
Q 10.
What is a wave number?
Q 11.
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 12.
Explain how the human ear works.
Q 13.
Obtain a relation between speed,frequency and wavelength of a wave.
Q 14.
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 15.
Fill in the blanks :
The product of wavelength of wave and its frequency gives _____________.
Q 16.
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 17.
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 18.
What travels faster : a rifle bullet or the sound of the shot fired from it ?
Q 19.
How does sound travel in gases and liquids as longitudinal or as transverse waves?
Q 20.
Distinguish between loudness and intensity of sound.
Q 21.
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 22.
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 23.
Explain the working and application of a sonar.
Q 24.
What is audible range ?
Q 25.
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 26.
What is the difference between an echo and a reverberation ?
Q 27.
Try to imagine what you would feel, what sort of person you would be,had you been born totally deaf.
Q 28.
What is Sound? Why it is important for us?
Q 29.
Why transverse wave does not travel through air or gases?
Q 30.
Calculate the wavelength of a sound wave having a frequency 300 Hz and speed 330 m/s.
Q 31.
Fill in the blanks :
RADAR (Radio Detection And Ranging) works on _____________ principle which is used to determine the velocities and movement of aircrafts.
Q 32.
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 33.
What is infrasonic? Give an example.
Q 34.
A periodic longitudinal Wave is sent on a slinky.The wave proceeds at a speed of 48 m/s and each particle oscillates at a frequency of 12 Hz.Calculate the minimum separation between the positions where the slinky is most compressed.
Q 35.
Guess which has a higher pitch : a guitar or a car horn ?
Q 36.
How are the wavelength and frequency of a sound wave related to its speed ?
Q 37.
Write the name of the wave which propagates in terms of compressions and rarefactions.
Q 38.
How are compressions and rarefactions produced near a source of sound ?
Q 39.
Fill in the blanks :
If a body repeats its motion, within fix interval of time, along a certain path, about a fixed point, it is said to have ____________.
Q 40.
What are wavelength, frequency, time period and amplitude of a sound wave?
Q 41.
Give an application use of ultrasonics.
Q 42.
What type of wave is represented by density- distance graph?
Q 43.
What is the audible range of the average human ear ?
Q 44.
What do you mean by reverberation and reverberation time ? How is reverberation controlled ?
Q 45.
Fill in the blanks :
Waves transport _________ not matter.
Q 46.
Write differences between Transverse waves and Longitudinal waves.
Q 48.
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 49.
The sonic boom of an aircraft has a time period of 0 00005 s.Calculate the frequency of the sound produced.
Q 50.
Radio Ceylon broadcasts at 25 m.What is the frequency of the station ?
