1. Sound : It is a mechanical energy which produces sensation of hearing.
2. Condition for the propagation of sound:
i) There must be vibrating body, carable of transferring energy.
ii) There must be a material medium, through which energy can propogate.
iii) There must be receiver(ear), so as to receive and transmit energy to brain.
3. Infra-sonic or sub-sonic vibrations : The vibration which are not perceived by human ear and have a range 0-20 Hz are called infra-sonic vibrations.
4. Sonic-vibrations: The vibration which produce sensation of hearing in human beings are called Sonic vibrations . Their range is between 20- 20000 Hz.
5. Ultra-sonic vibrations : The vibrations which are not perceived by human ear and their frequency range is above 20000 Hz are called ultra-sonic vibrations .
6. Bats navigate by emitting ultra-sonic vibrations and then receiving the echoes . Dogs and dolphins can also heer ultra-sonic vibrations .
7. Ultra-sonic vibrations are used in
i) homogenising milk and cosmetics.
ii) in dissipating fog.
iii) in dish cleaner
iv) Ultra-sound welding
v) ultra-sound scanning of human body.
8) Elastic waves: The waves produced in a material medium are called....
9) Transverse waves: When the particles of a medium vibrate at right angles to the direction of propagation of wave, then the wave so produced is called,...
10) Longitudinal wave: When the particles of a medium vibrate in the same direction in which a wave propagates , then such a wave is called....
11) Transverse wave is possible in solids only, whereas Longitudinal wave is possible in all kinds of material medium.
12) As a general rule, sound travels faster than solids, slower in liquids and slowest in gases.
13. The speed of the sound in solids and liquids at constant temperature is
i) directly proportional to square root of elasticity
ii) inversely proportional to square root of density of material.
14) The speed of sound in gases at constant temperature is given by v= √{γP/d}, where γ = 1.414; 'P' is the pressure of a gas and 'd' is the density of gas.
15) Speed of sound in air does not change with the change in
i) frequency
ii) wavelength
iii) amplitude
iv) pressure.
16. Speed of sound in air increases by 0.6 m/s for every 1°C rise in temperature.
17) Speed of sound in air increases with the increase in humidity and vice versa.
18) Speed of sound in air decreases with increase in density and vise versa.
19) Speed of sound in air increases if the direction of sound and wind are in same direction and vise versa.
20) Wave: The disturbance produced in a medium by the to and fro motion of its particles about their mean position is called...
21) Wave motion: The transfer of energy when the particles of a medium move about their mean positions is called wave motion.
22) Material wave or elastic waves: The waves produced in a material medium (solids; liquid or gases) by the movement of its particles about their mean positions are called material waves or elastic waves.
23) Characteristics of material medium for the propagation of sound:
i) it must be elastic.
ii) It must have least frictional resistance.
iii) It must possess inertia.
24) Amplitude: The maximum displacement of a particle about its mea position is called amplitude.
25) Frequency(f): The number of vibrations executed by a particle of a vibrating medium about its mean position in one second is called frequency.
OR
The number of waves passing through one particular point in one second is called the frequency.
26) Time period or periodic time (T): The time taken to complete one oscillation by any particle of a vibrating medium is called.....
27) Phase: The term used to describe the motion and direction of a vibrating particle, at some particular instant, during its course of motion is called phase .
28) Same phase: When two particles are moving exactly in the same way i.e., their displacement from mean position is same and so is direction, they are said to be in the same phase.
29) Opposite phase: When two particles are moving exactly in opposite way i.e., their displacement from mean position is same, but direction is opposite, they are said to be in opposite phase .
30) Out of phase: When the motion of the two particles in a vibrating medium is not similar in any respect, they are said to be out of phase.
31) Wave velocity (v): The distance covered by a disturbance in one second in some particular direction is called ...
32) Wavelength (λ): The linear distance between two consecutive particles of vibrating medium in the same phase is called....
OR
Linear distance covered by one complete wave is called....
QUESTIONS
1) State three conditions necessary for hearing sound sound.
2) Describe briefly an experiment to prove that vibrating bodies produce sound.
3) Name three animals which can hear ultra-sonic vibrations .
4) How do bats locate their prey during flight ?
5) What is Galton's whistle ? To what use it can be put ?
6) State four practical uses of ultra-sonic vibrations .
7) Describe an experiment to prove that material medium is necessary for the propagation of sound.
8) Why do the astronauts talk to each other through radio telephone in space or on the surface of moon?
9) What are electric waves ? Name two kinds of elastic waves.
10) Define the term longitudinal wave and show it diagrammatically.
11) State four characteristics of the longitududinal waves.
Characteristics:
12) Define the term transverse wave and show it by diagram.
13) State for characteristics of the transverse waves .
14) With reference to sound. which amongst the longitudinal wave and transverse wave is possible in a) solid b) gases ?
15) State four differences between longitudinal wave and transverse wave.
they consist of regions of compressions and rarefaction.
16) State three factors which determine the speed of sound in a material.
17) State the formula of speed of sound in solids.
18) State the formula of speed of sound in gases.
19) Amongst the air, carbon dioxide and helium, state in which material speed of sound is
a) Maximum
b) Minimum and why?
20) How is the speed of sound in air affected when the following parameters chang?
a) wavelength of sound wave increases.
b) pressure of air increases
c) temperature of air falls.
d) humidity in air increases.
e) Amplitude of sound wave decreases
f) the wind blows in the direction opposite to the direction of propagation of sound.
g) frequency of sound wave decreases.
h) The density of air increases, without any change in pressure.
21) How do the following affect, at all, the velocity of sound in air ?
a) pitch of sound
b) temperature of air
c) pressure of air.
d) moisture in air.
22) Give one example of longitudinal and transverse waves
23) The sound of an explosion on the surface of lake is heard by a boatman 100 m away and a driver 100 m below the point of explosion.
a) Of the two persons mentioned (boatman and diver), who would hear the sound first?
b) Give reason for your answer in (a).
c) If the sound takes 't' seconds to reach the boatman, approximately how much time it will take to reach the diver ?
24) State the important difference between light and sound waves.
25)) What is approximate value of the speed of sound in iron as compared to that in air ? Illustrate your answer with simple experiment.
26) How does a bat avoid obstacles in their way when in flight ?
27) A continuous disturbance is created on the surface of water in a ripple tank with a small piece of cork floating on it. Describe the motion of cork. What does motion of cork tell about disturbance .
28) Draw a displacement-time graph for water wave.
29) State any two characteristic of wave motion.
30) State three main characteristics of medium necessary for the propagation of sound waves.
31) Derive a relation between frequency and time period.
32) Derive a relation between wave velocity; frequency and wavelength.
33) The diagram shows a snap shot of a wave form of frequency 50Hz on a string. The numbers in diagram represent distance in centimetres.
For this wave motion find
a) Wavelength
b) Amplitude
c) wave velocity.
34) Draw a diagram representing a wave of
a) amplitude 4cm
b) wavelength 2m. if the frequency of wave is 150 Hz, calculate its velocity. 300ms⁻¹
35) The diagram shows a vibrating metal blade clamped at one end. P and R are the extreme positions occupied by the blade during its course of vibration. Q, being its position of rest. The vibrating blade produces a note of 480 Hz.
i) Mark the diagram amplitude of vibration.
ii) if the velocity of the sound in air is 320 ms⁻¹, what is the wavelength of sound produced ? 0.66 m
36) Explain why lightning flash is seen before the crack of thunder.
NUMERICAL PROBLEMS
1) The speed of the sound at 4° C is 322.4 ms⁻¹. Calculate the speed of sound at 34° C. 340.4 ms⁻¹
2) The speed of sound at -5°C is 317ms⁻¹. Calculate the speed of sound at
a) 35°C. 341ms⁻¹
b) - 45° C. 293 ms⁻¹
3) The speed of sound at 0° C is 320 ms⁻¹. Calculate the temperature when speed of sound
a) increases by 1/8th of speed of sound at 0°C. 66.67°C
b) decreases by 1/12th of speed of sound at 0°C. -44.45°C
4) The speed of sound at 10°C is 326 ms⁻¹. Calculate the temperature at which speed of sound is 302ms⁻¹. -30°C
5) A sound wave of frequency 640 Hz travels 800 m in 2.5s. Calculate
a) speed of sound. 320ms⁻¹
b) wavelength of sound wave. 0.5m
6) A television station broadcasts at a frequency of 4500 MHz. If the speed of television waves is 3 x 10⁸ ms⁻¹. Calculate the wavelength of television waves. 0.067 m
7) A longitudinal wave of wavelength 0.03 cm travels in air with a speed of 330ms⁻¹.
Calculate the frequency of the wave. Can this wave be heard by normal human ear. Give a reason for your answer. 1100000 Hz, The above wave cannot be heard. It is because, the maximum range to which human ear can hear is 20000 Hz. As the frequency of 1100000 Hz is far in excess thereore it will not produce any sound effect in ear.
8) a sound wave as a frequency of 2000 wavelength 17 if the wavelength increases by 51 what is the frequency the nature of the material through which sound is propagation remains of 22 a disturbance in here as were length of 22 and speed calculate the frequency of disturbance state whether they were disturbance is audible normal human ear give one reason for your answer ultraviolet radiation is wavelength 150 + the ultraviolet radiation is 3 calculate the frequency of radiation time period the web length of the waves produced on the surface of the water is 20 the way velocity is 24 calculate the number of produced in 1 second time required to produce one web ET metal plate is placed again if the cogil is rotted at a constant speed of 360 rotation per minute calculate the frequency of a note produce speed of the sound if the wavelength 0.7 what will be the refractive the speed of the cow will be hacked in turning for can produce a lot of problem 0.83 and has a time period of 2.5 into 10 seconds calculate the web velocity the distance between 1 crest and one trap produce on the surface of water is 0.04 if the waves are produced at the rate of 184 M calculate time period and web velocity
A) Fill the blanks:
1) Sound is produced due to the-- in the medium
2) Sound requires a -- to travel.
3) Bats detect obstacles in their path by receiving the reflected...
4) The note of the lowest frequency for a vibrating string is called....
5) Quality of sound depends upon.. frequencies.
6) To hear the echo of a sound, the reflecting surface should be at a minimum distance of---
7) The pitch of sound .... if the frequency is increased.
8) The Intensity of sound is ....to the square of the amplitude of wave.
9) The sound becomes... if amplitude is increased.
10) Resonance is a special case of... vibrations, when frequency of the driving force is ...to the natural frequency of the body.
B) State whether True/False. Also correct the false statements.
1) The sound heard after reflection from a rigid obstacles is called an echo.
2) Resonance occurs when natural frequency of a body is less than the frequency of the applied force.
3) The vibration of a body with constant amplitude and constant frequency are called forced vibrations.
4) The frequency of vibrations of air column is directly proportional to the length of the air column.
5) The loudness is a measurable quantity while intensity is a sensation.
6) The pitch of sound increases if it's frequency increases.
C) Answer the following
1) a) Define echo.
b) State two conditions necessary
for an echo.
c) Write its use.
2) What is vibrated to produce sound in :
a) a violin
b) an organ pipe
c) a drum
3) Define:
a) Free vibrations of a body ?
b) Forced vibrations?
4) Define Resonance. State the condition necessity for resonance to occur.
5) State the physical quantity whose unit is decibel. Name another unit of this physical quantity.
6) Are intensity and loudness the same ?
7) Name three characteristics of a musical sound.
8) What determines the pitch of a sound ?
9) State one factor that determines the quality of a musical note.
10) a)What is Sonar ?
b) State the principle on which it is bases .
c) State its uses.
11) Write a relation between the velocity of sound and distance of source of sound from reflecting body and time for hearing an echo.
12) Name the subjective Property of sound related to its frequency.
13) Give one example each of
a) Natural vibration
b) Forced vibration
c) Resonance
14) A turning fork held over an air column of a given length, produces a distinct audible sound. What do you call this phenomenon? How does it occur ?
15) How can one distinguish the sound of two musical instruments even if they are of the same pitch and the same loudness ?
16) How is the speed of sound in air affected when the following parameters change?
A) Wavelength of sound wave increases
B) Pressure of air increases
C) Temperature of air falls
D) Humidity of sound wave increases
E) Amplitude of sound wave decreases
F) Frequency of sound wave decreases
17) What change, if any, would you expect in the characteristics of a musical sound when we increase
A) Its frequency
B) Its amplitude
REASON BEHIND:
1) The rear view mirror of a motor bike starts vibrating violently at some particular speed of the motor bike.
A) Why does this happen?
B) What is the name of the phenomenon taking place?
C) What could be done to stop the violent vibrations?
2)A) How does a stretched string on being set into vibration, produce an audible sound?
B) will this sound be audible if the string is set into vibration on the surface of the moon? Give reason for your answer?
3) Women's voice is shriller than men's voice.
4) Why lightening flash is seen before thunder is hard ?
5) why are the stringed instruments provided with a sound box?
6) Why is bell provided with a big outer case?
7) Two friends were playing on their identical guitars whose strings were adjusted to give notes of the same pitch. Will the quality of the two notes by the same? Give a reason for your answer?
8) We can recognise our friends even by listening to their voices.
9) A renowned singer's voice is sweeter.
10) It is not possible to talk through an open space.
11) How a megaphone can help in making the sound heard at a distance OR Why do we cup our hands to make the sound heard at a distance.
12) Windows sometimes rattle when the low notes of pipe organ are sounded.
13) Tick, Tick of watch is not musical while buzzing of a bee is.
14) Why is a loud sound head at acoustic resonance
15) Why echo can't be heard in a small room
16) Why can we hear echoes in long galleries and big halls?
17) Bat have no eyes still they can ascertain distances, directions nature and size of the object.
18) Why soldiers asked to walk out of step while crossing bridges
19) How does frequency and amplitude affect a musical sound?
20) Why strings of different thickness are provided on a stringed instrument.
21) A vibrating turning fork is placed over the mouth of a burette filled with water, the tap is opened and the water level gradually falls. It is observed that the sound becomes the louder for a particular length of air column.
A) What is the name of the phenomenon taking place when this happens?
B) Why does the sound become the loudest?
C) What is the name of the phenomenon taking place when sound is produced for another length of air column and is not loudest?
DIFFERENCE BETWEEN
A) Musical note/Noise
B) Resonance/Forced vibrations
C) Free vibrations/Forced vibrations
