Q.1 How does a sound making object differ from one that is
silent?
Answer: Sound making object can vibrate easily.
Q.2 How does sound from a sound producing body travel
through air to reach our ears?
Answer: Sound
from a sound producing body travel through air to reach our ears by making
regular compression and rarefaction.
Q.3 Why are the voices of men, Women and children different?
Q.3 Why are the voices of men, Women and children different?
Answer: The
voices of men, women and children differ from each other due to the following
factors:
1) The pitch is
one of the most essential factors to determine the voice of the individual. For
example, men have lower-pitched voices while women have higher-pitched voices.
2) Second
factor which brings in the difference in the voices is the length and the
thickness of vocal cords.
Q.4 Why a sound cannot be heard on the moon?
Answer: A sound
cannot be heard on the moon due to absence of medium air
Q.5 How do astronauts talk to one another on the
surface of moon and Why?
Answer: Astronauts communicate with the help of radio waves on moon because these waves do not need a medium to travel
Answer: Astronauts communicate with the help of radio waves on moon because these waves do not need a medium to travel
Q.6 If you want to hear a train approaching from far
away, why is it more convenient to put the ear to the track?
Answer: This is because sound can travel through railway track (solid ) faster than through air.
Answer: This is because sound can travel through railway track (solid ) faster than through air.
Q.7 State one observation from everyday life which
shows that sound travels much more slowly than light?
Answer: We hear thunder after lightining.
Answer: We hear thunder after lightining.
Q.8 What is the scientific name for the
following? The number of vibrations made per second.
Answer: Frequency
Answer: Frequency
Q.9 Why do we not hear the screams of a bat?
Ans: This is because
the screams are ultra sonic(above 20,000 hertz) which human ear cannot hear.
Q.10 Which of the following frequency of sound can be heard by a dog but not by a man? (a) 50,000 hertz (b) 15,000 hertz
Answer: A sound of frequency 50,000 hertz can be heard by a dog but not by a man
Q.10 Which of the following frequency of sound can be heard by a dog but not by a man? (a) 50,000 hertz (b) 15,000 hertz
Answer: A sound of frequency 50,000 hertz can be heard by a dog but not by a man
Q.11 Explain how, noise pollution {or excessive loud noise}
is harmful to human beings.
Answer: Noise pollution can lead to a number of health-related problems. Some of them are as follows:
Answer: Noise pollution can lead to a number of health-related problems. Some of them are as follows:
(i) Hearing
loss (ii) inability to sleep (iii) Hypertension (iv) Severe headache (v) Stress
Q.12 State the various measures which can be taken to
control {or reduce} noise pollution in our surroundings.
Answer: Noise pollution can be reduced by using silencers in vehicles, industrial machines, and home appliances reducing use of vehicle horns, running TV, radio and music systems at low volumes. Planting of trees along roads and buildings also help to reduce noise pollution.
Answer: Noise pollution can be reduced by using silencers in vehicles, industrial machines, and home appliances reducing use of vehicle horns, running TV, radio and music systems at low volumes. Planting of trees along roads and buildings also help to reduce noise pollution.
Q.13 Give two causes of noise pollution from the homes.
Answer: . In the home noise pollution is caused by television radio and music systems at high volume, some kitchen appliances, desert coolers, air conditioners etc.
Answer: . In the home noise pollution is caused by television radio and music systems at high volume, some kitchen appliances, desert coolers, air conditioners etc.
Q.14 Sound of different pitch can be produced using a
flute. Explain, how?
Answer: If
we blow a flute, the air column vibrates and produces sound. Flute contains
small air columns, when air is bowed through the mouth piece the air columns
start vibrating which produces sound.
Q.15.How does Sound produced by
humans?
Answer: In humans sound is produced by the vioce
box or larynx. It is the upper part of the wind pipe. Two vocal cords are
stretched across the voice box leaving a narrow slit. When the lungs force air
through the slit, it vibrates and produces sound.
Q. 16. How Jal Tarang produces sound?
Answer: In Jal-tarang
musical instrument the cup containing minimum water produces the sound of
lowest frequency or lowest pitch. As the amount of water in the cup goes on increasing,
the frequency (or the pitch) of the sound produced also goes on increasing.
Q. 17. If 125 oscillations are produced in 5 seconds, what
is the frequency in hertz?
Answer: in 5 seconds
125 oscillations are produced
So, in 51 seconds
125/5 = 25 oscillations are produced
Hence, the
frequency = 25Hz
Q. 18. What is the
frequency of a vibrating body whose time-period is 0.05 second?
Answer: f = 1/t = 1/0.05 = 100/5 = 20HZ
Q. 18. State true or false
(i) Sound can be produced by beating an object
irrespective of whether there are vibrations or not.
(ii)The sound of a tabla normally has a lower
pitch than the sound of a violin.
(ii)A short flute will produce sound of lower
pitch than a long flute.
Answer: (i) –False [Sound is produced from a vibrating object.]
(ii) -True [The sound of a tabla normally has a lower pitch than the
sound of a violin.]
(iii) –True[A short flute will produce sound of lower pitch than a
long flute.]
Q.19. Give reasons Why Trees planted along the
roads reduce noise?
Answer: Trees are planted along the roads and around buildings so
that it could cut off sound vibrations produced from vehicles speakers etc. by absorbing
them, hence leading in prevention of Noise pollution.
Q.20. what are transverse and longitudinal waves?
Answer: Longitudinal waves: A wave in which the particles of the
medium vibrate back and forth in the same direction in which the wave is moving
is called longitudinal wave. Example: sound waves.
Transverse waves: A wave in which the particles of the medium
vibrate at right angles to the direction, in which the wave is moving, is
called transverse wave. Example: Light waves.
1. How sound is produced?
2. What do you understand by a ‘wave’?
3. Write three differences between sound and light waves.
4. What do you understand by “sound energy cannot be produced”?
5. What is the name of the wave that can travel through vacuum?
6. Explain by some experiment that sound waves require medium for their propagation.
7. How sound waves travel through some medium?
8. Why sound waves do not propagate through vacuum?
9. What are the transverse waves? Give two examples.
10. What are longitudinal waves? Give two examples.
11. Give two points of difference between longitudinal and transverse waves.
12. How will you prove that the sound waves exhibit longitudinal behaviour?
13. What are rarefaction and compression in case of sound waves?
14. Distinguish between crests and troughs.
15. Write the SI unit of velocity of a wave.
16. What are the factors that describe the sound wave and define them?
17 Why is a thundering sound heard later than lightening?
18. Sound travels with different speeds in different media. Comment.
19. How far is a compression and its nearest rarefaction in a longitudinal wave?
20. Define sound ranging.
21. What is the frequency range of sound for human beings?
22. What are the ultrasonic and supersonic waves?
23. What type of waves are produced by animals like bats and dolphins?
24. Explain two applications of ultra sound waves?
25. Explain how ultrasound waves are used to detect a flaw in an object?
26. Which sound wave is used in ECG (echocardiography)?
27. Give the full form of SONAR.
28. Name the technique used to measure the depth of a sea.
29. How will you determine the depth of a sea using SONAR?
30. How do the bats fly in dark?
31. How RADAR is different from SONAR?
32. Explain the function of ear by explaining its each part.
2. What do you understand by a ‘wave’?
3. Write three differences between sound and light waves.
4. What do you understand by “sound energy cannot be produced”?
5. What is the name of the wave that can travel through vacuum?
6. Explain by some experiment that sound waves require medium for their propagation.
7. How sound waves travel through some medium?
8. Why sound waves do not propagate through vacuum?
9. What are the transverse waves? Give two examples.
10. What are longitudinal waves? Give two examples.
11. Give two points of difference between longitudinal and transverse waves.
12. How will you prove that the sound waves exhibit longitudinal behaviour?
13. What are rarefaction and compression in case of sound waves?
14. Distinguish between crests and troughs.
15. Write the SI unit of velocity of a wave.
16. What are the factors that describe the sound wave and define them?
17 Why is a thundering sound heard later than lightening?
18. Sound travels with different speeds in different media. Comment.
19. How far is a compression and its nearest rarefaction in a longitudinal wave?
20. Define sound ranging.
21. What is the frequency range of sound for human beings?
22. What are the ultrasonic and supersonic waves?
23. What type of waves are produced by animals like bats and dolphins?
24. Explain two applications of ultra sound waves?
25. Explain how ultrasound waves are used to detect a flaw in an object?
26. Which sound wave is used in ECG (echocardiography)?
27. Give the full form of SONAR.
28. Name the technique used to measure the depth of a sea.
29. How will you determine the depth of a sea using SONAR?
30. How do the bats fly in dark?
31. How RADAR is different from SONAR?
32. Explain the function of ear by explaining its each part.
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