The comprehensive approach in SCERT Class 10 Physics Solutions Chapter 1 Sound Waves Important Questions with Answers ensure conceptual clarity.
SSLC Physics Chapter 1 Important Questions Kerala Syllabus
Sound Waves Class 10 Important Questions
Question 1.
Classify the following statements as transverse wave and longitudinal wave.
a) Particles of the medium vibrate perpendicular to the direction of propagation of the wave.
b) Creates pressure difference in the medium
c) Forms in solids, liquids and gases
d) Light waves
e) Seismic waves
f) Forms crest and trough
Answer:
Transverse wave: a, d, f
Longitudinal wave: b, c, e
Question 2.
Complete the word pair
Transverse waves : Crests and troughs
Longitudinal waves : ………………………….
Answer:
Compressions and rarefactions
Question 3.
Bats make use of …………………….. sounds for catching prey.
Answer:
Ultrasonic
Question 4.
What kind of waves are used in sonar? Write one use of these waves in the medical field.
Answer:
Ultrasonic waves, to crush small stones in the kidney.
Question 5.
Given below are graphs of sound waves from different sources that travels through the same medium. Among these, which one has higher frequency? What is the basis of your conclusion?
Answer:
Wave with higher frequency is shown in graph B. As both travel through the same medium, velocity remains the same. But wavelength is inversely proportional to the frequency. ‘B’ has lower wavelength, so B itself has higher frequency.
Question 6.
A sound wave enters water from air. What happens to its wavelength? Why?
Answer:
Wavelength increases. Velocity of sound in water is 1482 m/s and velocity in air is 343 m/s. But the frequency of the sound wave will not change as the medium differs. We know V = f λ. So wavelength should increase.
Question 7.
Given in the graph the points A, B, C, D represents state of vibration of a sound wave. From the below mentioned options which represent the wavelength.
a) Distance between A and C
b) Distance between A and D
c) Distance between A and B
d) Distance between B and C
Answer:
a) Distance between A and C
Question 8.
The wave length of sound travelling in air with the velocity 330 m/s was found to be 60 m. If so
a) Find the frequency of sound.
b) By what name are sounds of such frequency known as?
Answer:
a) V = fλ
330 = f × 60
f = \(\frac{330}{60}\) = 5.5 Hz
b) Infrasonic sound, (frequency is less than 20 Hz)
Question 9.
Velocity of sound in air is 340 m/s. Sound waves of wavelength 0.01 m from a vibrating body reach your ear through air. Will you be able to hear the sound? Justify your answer.
Answer:
V = 340m/s
λ = 0.01m
V = fλ
f = \(\frac{V}{\lambda}\)
f = \(\frac{340}{0.01}\) = 34000 Hz > 20,000 Hz
Human beings cannot hear these sounds.
Audible frequency range of humans is 20 Hz to 20000 Hz.
Question 10.
The tuning fork is stimulated at a frequency of 3 84 Hz and its shaft is pressed to the table at a natural frequency of 230 Hz.
a) Will the table vibrate in this case?
b) Will there be a change in the loudness of the sound? What is the reason?
Answer:
a) The table will vibrate.
b) When the stem of the excited tuning fork is placed on the table, the table vibrates by the impulse of the tuning fork. The more the area of the table, the louder the sound. In this case, the sound became louder because the table also vibrated along with the tuning fork.
Question 11.
A tuning fork with a frequency of 512 Hz is stimulated and held at the mouth of a resonance column. Then there is a slight increase in the pitch of the sound.
a) What is the vibration of the air inside the resonance column called?
b) What is the frequency of the air when the noise level is the highest?
Answer:
a) A forced vibration
b) 512 Hz
Question 12.
Match correctly
| Sound Board | Resonance |
| Resonance Column | Period |
| Characteristic of wave | Richter scale |
| Intensity of earthquake | Reflection of sound |
Answer:
| Sound Board | Reflection of sound |
| Resonance Column | Resonance |
| Characteristic of wave | Period |
| Intensity of earthquake | Richter scale |
Question 13.
Write 4 uses of ultrasonic waves.
Answer:
- To crush small stones in the kidneys.
- In physiotherapy.
- To take images of internal organs such as kidney, liver, gall bladder and uterus.
- For cleaning spiral tubes, irregular machine parts, electronic components etc.
Question 14.
What are the uses of sonar?
Answer:
- Sonar is used to find the distance to the underwater objects.
- It is used to measure the depth of the ocean.
- Used to find the location of fish flocks.
Question 15.
A sound signal of 50 kHz is sent to the bottom of a sea. It returned back after 4 s. The velocity of sound in seawater is 1500 m/s. Then,
a) Calculate the depth of the sea
b) What is the wavelength of the wave?
Answer:
a) Suppose the depth of the sea = d
then distance travelled by the wave = 2d
distance = velocity × time
= 1500 × 4
= 6000 m
.’. depth= \(\frac{6000}{2}\) = 3000 m
b) V = fλ
V = 1500 m/s
f = 50kHz = 50000 Hz
λ = \(\frac{v}{f}\) = \(\frac{1500}{50000}\)
Question 16.
A sound was produced. Three seconds later, its echo was heard.
a) What is the distance between the reflecting surface and source? (Speed of sound in air is 340 m/s)
b) Write two methods by which you can reduce the harmful effects of reflection of sound in big halls.
Answer:
a) Distance = Velocity × time
= 340 × 3 = 1020 m
So distance between the source and reflecting surface = \(\frac{1020}{2}\) = 510 m
b) Make the walls rough, provide a large number of ventilators.
Question 17.
a) Sound waves from SONAR in a ship hits the bottom of the sea and comes back after is 1/2 s. Calculate the distance to the bottom of the sea from the ship. (Speed of sound in sea water is 1522 m/s)
b) Which type of sound waves is used in SONAR?
Answer:
a) v = \(\frac{s}{t}\)
v = 1522 m/s
t = \(\frac{1}{2}\)s
s = v × t
= 1522 × \(\frac{1}{2}\)
= 761 m
b) Ultrasonic waves.
Question 18.
Find the reason.
a) The walls are made rough in movie theaters, halls and auditoriums.
b) Soldiers are not allowed to march through the hanging bridge.
Answer:
a) The walls are made rough to avoid the regular reflection of sound. Rough surfaces can absorb sound.
b) If the frequency of vibrations generated as a result of continuous marching is equal to the natural frequency of the bridge, then there is a possibility of the bridge vibrating at a high rate and collapsing. That is, the soldiers are not allowed to march through the hanging bridge to avoid the danger that occurs when the frequency of marching coincides with the natural frequency of the bridge.
Question 19.
The sound signal from a ship on the water surface hits the underwater rock and returns to the ship after 6 s. The speed of sound in sea water is 1522 m/s.
a) What type of wave is transmitted in the sound?
b) What is the cause of the return of the sound signal to the ship?
c) Calculate the distance from the water surface to the rock.
Answer:
a) Longitudinal wave
b) Reflection of sound
c) Speed of sound = total distance traveled / time
Total distance traveled = speed of sound × time
2d = v × t
d = (v × t) / 2 = (1522 × 6) / 2 = 4566 m.
Question 20.
Explain the technique ultra sonography?
Answer:
Ultrasonic waves that travel through body tissues strike and reflect at areas of varying density in the tissues. These waves are converted into electric signals to form an image of the organ. This technique is ultra sonography.
Question 21.
Observe the figure
a) What kind of wave motion is shown in the figure? Illustrate your answer
b) Calculate the frequency of this wave if its velocity is 6420 m/s and wavelength is 6 m.
Answer:
a) Longitudinal wave.
Here pressure difference is plotted against the y axis. Pressure difference forms only in longitudinal waves
b) V = 6420 m / s
λ = 6 m
frequency, f = \(\frac{V}{\lambda}\)
= \(\frac{6420}{6}\) = 1070 Hz
Question 22.
List the waves given below as appropriate.
• Seismic waves
• Light waves
• Sound waves
• Radio waves
• Waves formed on water surface
Answer:
| Those which need a medium for propagation | Those which do not need a medium for propagation |
| • Seismic waves • Sound waves • Waves formed on water surface |
• Radio waves • Light waves |
Question 23.
Figure shows the distance and displacement of a wave formed in 0.2 s.
a) What is its wavelength?
b) What is the frequency?
c) What is its velocity?
Answer:
a) 5 m
b) f = \(\frac{n}{t}\) = \(\frac{3}{0.2}\) = 15 Hz
c) V = fλ = 15 × 5 = 75 m/s
Question 24.
Observe the figure
a) Which particle is in the same phase of vibration as that of B?
b) What is the distance between these particles called?
c) If the distance between C and E is 25 m, what is the wavelength?
Answer:
a) F
b) wavelength
c) 50 m
Question 25.
Observe the figure
a) How many trough are there?
b) Find out the wavelength?
c) Calculate velocity of the wave if it is travelled within 0.02s.
Answer:
a) 3
b) 4 m
c) f = \(\frac{n}{t}\) = \(\frac{3}{0.02}\) = \(\frac{300}{2}\) = 150 Hz
V = fλ
= 150 × 4 = 600 m/s
Question 26.
A graphic illustration of a wave is given.
a) What type of wave is seen in the picture?
b) What is the amplitude of the wave?
c) If it takes 3 s to go from A to B, what is the frequency?
d) Find the velocity.
Answer:
a) Transverse wave
b) 2 cm
c) frequency = 1 Hz
d) v = fλ = 1 × 6 = 6 m/s
Question 27.
What are the methods to be adopted to escape from Tsunami? Discuss.
Answer:
- Move to a higher plain taking the unusual receding of the sea from the sea shore as a warning of the approaching Tsunami.
- Don’t assume for yourself that the danger is over, instead, wait for the official announcement.
- Try to save your life and not your belongings, as life is precious.
- If caught in Tsunami, try to save yourself by latching onto some floating objects.
Question 28.
Graphic illustration of transmission of two transverse waves A and B through air at a particular time.
If the waves travel this distance in 4 s,
a) Compare the speed of the waves.
b) Write the wavelength of each wave.
e) Which wave has the highest frequency?
d) Write the frequencies of A and B waves.
e) How far will the wave travel in 6 s?
Answer:
a) The speed of the two waves is equal.
b) The wavelength of A = 8 m
The wavelength of B = 4 m.
c) B
d) Frequency of A = 2 cm
Frequency of B = 2 cm
e) Distance traveled in 6 s = (16/4) × 6 = 24 m.
Question 29.
Observe the graphic representation of a wave motion given below.
a) The type of wave is …………………… (Transverse / Longitudinal)
b) Amplitude of the waves is …………………… (1 cm / 2 cm)
c) Wavelength of the wave is …………………… (4m/ 8m)
d) If the waves takes 3 s to reach A, frequency of the waves is …………………… (3 Hz/ 1 Hz )
e) Number of crests is …………………… (3/6)
f) Number of troughs is …………………… (3/2)
g) Speed of the wave is …………………… (8 m/s, 24 m/s )
h) Example for this type of wave is …………………… (Light wave / Sound wave)
Answer:
a) Transverse
b) 2 cm
c) 8 m
d) 1 Hz
e) 3
f) 3
g) 8 m/s (v = f λ = 1 × 8 = 8 m/s)
h) Light wave
Question 30.
SI unit of period is …………………….
Answer:
second
Question 31.
Define frequency with its unit?
Answer:
The number of oscillations in one second is called frequency. The SI unit of frequency is hertz (Hz).
Question 32.
Write the factors that influence the natural frequency of an object?
Answer:
- Length of the object
- Size of the object
- Elasticity
- Nature of the material
Question 33.
What is meant by the term oscillation?
Answer:
Oscillation is a periodic motion in which an object moves to and fro at regular intervals of time about its equilibrium position.
Question 34.
List whether what happens in each of the following cases is a natural vibration or a forced vibration.
a) Vibration of the stimulated tuning fork
b) The vibration of the sound board during the recovery of the falls
c) The vibration of the air inside the ball when it hits the ball
d) The vibration when the coin falls to the ground
e) The vibration of a steel vessel when it is struck with a spoon
Answer:
| Natural Vibration | Forced Vibration |
| a) Vibration of the stimulated tuning fork | b) The vibration of the sound board during the recovery of the falls |
| d) The vibration when the coin falls to the ground | c) The vibration of the air inside the ball when it hits the ball |
| e) The vibration of a steel vessel when it is struck with a spoon |
Question 35.
Below is a picture of hexoblades of various lengths fixed on a wooden board.
a) Which blade vibrates in the same way as the blade of C is excited?
b) Why do the two blades vibrate in the same way?
c) What is the vibration of the other blades known as?
Answer:
a) F
b) The natural frequency of both is equal because of resonance.
c) Forced Vibration
Question 36.
What happens to the amplitude of vibrations when the natural frequency of an object matches the frequency of the external forcing object?
Answer:
If the natural frequency of the forcing object and that of the forced object are equal, the objects are said to be in resonance. The objects undergoing resonance will vibrate with maximum amplitude.
Question 37.
Select and write the statements which are suitable for longitudinal waves.
a) The particles of the medium vibrate in a direction perpendicular to the direction of propagation.
b) Propagated by compressions and rarefactions.
c) Sound waves
d) Ripples formed on still water surface.
e) The particles of the medium vibrate in a direction parallel to the direction of propagation.
f) Wavelength is measured as the distance between two consecutive crests or troughs.
Answer:
(b), (c), (e)
Question 38.
Classify the following in the given table
| Those which need a medium for propagation | Those which do not need a medium for propagation |
a) Radio waves
b) Waves formed on water surface
c) Sound waves
d) Light waves
Answer:
| Those which need a medium for propagation | Those which do not need a medium for propagation |
| b) Waves formed on water surface | a) Radio waves |
| c) Sound waves | d) Light waves |
Question 39.
Electromagnetic waves are ………………… waves, (longitudinal / transverse)
Answer:
transverse
Question 40.
Find the one that doesn’t belong to the group and write the reason.
Amplitude, wavelength, speed of wave, equilibrium position
Answer:
Equilibrium position. Because all others are characteristics of waves.
Question 41.
Write the wave equation. What do each of the letters stand for?
Answer:
Speed of light = frequency × wavelength
v = fλ
where v – the speed of light, f – frequency, λ – the wavelength
Question 42.
Figure shows the distance – displacement graph. The wave is formed in 2s.
a) What is its amplitude?
b) What is its wave length?
c) What is its frequency?
d) What is its velocity?
Answer:
a) 0.2 m
a) 4 m
c) f = \(\frac{n}{t}\) = \(\frac{4}{2}\) = 2Hz
d) V = fλ = 2 × 4 = 8m/s
Question 43.
Distinguish between reverberation and echo.
Answer:
Reverberation is the persistence of sound as a result of multiple reflection. Echo is the phenomenon of hearing a sound by reflection from a surface or obstacle, after hearing the original source.
Question 44.
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A person standing at A claps his hands. Is there any change for occurring echo?
Answer:
Yes, can hear echo. Because the wall w2 is 18m away from the source. Minimum distance to hear echo is 17m.
Question 45.
A person who bursts a cracker hears its echo after 1 S. How far is the reflecting surface from the person hearing the echo? (speed of sound in air is 340 m/s).
Answer:
Let d be the distance to the reflecting surface. Then the total distance travelled by the sound to the reflecting surface and back will be 2d.
Speed of sound = \(\frac{\text { Total distance travelled }}{\text { Time }}\)
v = \(\frac{2 \mathrm{~d}}{t}\)
d = \(\frac{(\mathrm{v} \times \mathrm{t})}{2}\) = \(\frac{(340 \times 1) \mathrm{m}}{2}\) = 170 m
So the reflecting surface will be 170 m away.
Question 46.
What does seismology mean?
Answer:
Seismology is the study of seismic waves.
Question 47.
Which instrument is used to measure the intensity of earthquake?
Answer:
Richter scale
Question 48.
What are the consequences of earthquakes?
Answer:
- Damage to buildings.
- Traffic routes are disrupted.
- Dams are collapsed.
- Trees fall to the ground.
- It causes loss of life and property.
- It causes tsunami.
Question 49.
Define tsunami.
Answer:
Tsunami is a series of gigantic ocean waves caused by the displacement of large volumes of water in the sea.