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Question 1. Explain how sound is produced
by your school bell.
Question 2. Why are sound waves called
mechanical waves?
Question 3. Suppose you and your friend are
on the moon. Will you be able to
hear any sound produced by
your friend?
Question 1. Which wave property determines
(a) loudness, (b) pitch?
Question 2. Guess which sound has a higher
pitch: guitar or car horn?
Question 1. What are wavelength, frequency,
time period and amplitude of a
sound wave?
Question 2. How are the wavelength and
frequency of a sound wave
related to its speed?
Question 3. Calculate the wavelength of a
sound wave whose frequency is
220 Hz and speed is 440 m/s in
a given medium.
Question 4. 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?
Question 1. In which of the three media, air,
water or iron, does sound travel
the fastest at a particular
temperature?
Question 1. An echo returned in 3 s. What is
the distance of the reflecting
surface from the source, given
that the speed of sound is
342 m s–1?
Question 1. Why are the ceilings of concert
halls curved?
Question 1. What is the audible range of the
average human ear?
Question 2. What is the range of frequencies
associated with
(a) Infrasound?
(b) Ultrasound?
Question 1. A submarine emits a sonar pulse,
which returns from an
underwater cliff in 1.02 s. If the
speed of sound in salt water is
1531 m/s, how far away is the
cliff?
Question 1. What is sound and how is it produced?
Question 2. Describe with the help of a diagram, how compressions and
rarefactions are produced in air near a source of sound.
Question 3. Cite an experiment to show that sound needs a material
medium for its propagation.
Question 4. Why is sound wave called a longitudinal wave?
Question 5. Which characteristic of the sound helps you to identify your
friend by his voice while sitting with others in a dark
room?
Question 6. Flash and thunder are produced simultaneously. But thunder
is heard a few seconds after the flash is seen, why?
Question 7. A person has a hearing range from 20 Hz to 20 kHz. What are
the typical wavelengths of sound waves in air corresponding
to these two frequencies? Take the speed of sound in air as
344 m s–1.
Question 8. Two children are at opposite ends of an aluminium rod. One
strikes the end of the rod with a stone. Find the ratio
of times
taken by the sound wave in air and in aluminium to reach the
second child.
Question 9. The frequency of a source of sound is 100 Hz. How many times
does it vibrate in a minute?
Question 10. Does sound follow the same laws of reflection as light does?
Explain.
Question 11. When a sound is reflected from a distant object, an echo is
produced. Let the distance between the reflecting surface and
the source of sound production remains the same. Do you
hear echo sound on a hotter day?
Question 12. Give two practical applications of reflection of sound waves.
Question 13. A stone is dropped from the top of a tower 500 m high into a
pond of water at the base of the tower. When is the splash
heard at the top? Given, g = 10 m s–2 and speed of sound =
340 m s–1.
Question 14. A sound wave travels at a speed of 339 m s–1. If its wavelength
is 1.5 cm, what is the frequency of the wave? Will it be audible?
Question 15. What is reverberation? How can it be reduced?
Question 16. What is loudness of sound? What factors does it depend on?
Question 17. Explain how bats use ultrasound to catch a prey.
Question 18. How is ultrasound used for cleaning?
Question 19. Explain the working and application of a sonar.
Question 20. A sonar device on a submarine sends out a signal and receives
an echo 5 s later. Calculate the speed of sound in water if the
distance of the object from the submarine is 3625 m.
Question 21. Explain how defects in a metal block can be detected using
ultrasound.
Question 22. Explain how the human ear works.
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