Class 8: Physics Chapter 7 solutions. Complete Class 8 Physics Chapter 7 Notes.
Selina Class 8 ICSE Solutions Physics : Chapter 7- Sound
Selina 8th Physics Chapter 7, Class 8 Physics Chapter 7 solutions
A. Objective Questions
1. Write true or false for each statement
(a) When sound propagates in air, it does not carry energy with it.
Solution: False.
(b) In a longitudinal wave, compression and rarefaction are formed.
Solution: True.
(c) The distance from one compression to the nearest rarefaction is called wavelength.
Solution: False.
(d) The frequency is measured in second.
Solution: False.
(e) The pitch of a sound depends on the amplitude of the wave.
Solution: False.
(f) The pitch of a sound depends on the amplitude of the wave.
Solution: True.
(g) Decibel is the unit of the pitch of a sound.
Solution: False.
Question 2
Fill in the blanks
(a) The time period of a wave is 2 s. Its frequency is 0.5S-1
(b) The pitch of a stringed instrument is increased by increasing tension in the string.
(c) The pitch of a flute is decreased by increasing the length of the air column.
(d) Smaller the membrane, higher is the pitch.
(e) If a drum is beaten hard, its loudness increases.
(f) A tuning fork produces the sound of a single frequency.
Question 3
Match the following
Column A Column B
(a) Amplitude (i) 1/time period
(b) Frequency (ii) amplitude
(c) Loudness (iii) maximum displacement
(d) Pitch (iv) presence of other frequencies
(e) Waveform (v) frequency
Solution:
Column A Column B
(a) Amplitude (iii) maximum displacement
(b) Frequency (i) 1/time period
(c) Loudness (ii) amplitude
(d) Pitch (v) frequency
(e) Waveform (iv) presence of other frequencies
Question 4
Select the correct alternative
(a) Sound can not travel in
1. solid
2. liquid
3. gas
4. vacuum
Answer: The correct answer is 4. vacuum
(b) When sound travels in the form of a wave
1. the particles of the medium move from the source to the listener
2. the particles of the medium remains stationary
3. the particles of medium start vibrating up and down
4. the particles of medium transfer energy without leaving their mean positions.
Answer: The correct answer is 4. the particles of medium transfer energy without leaving their mean positions.
(c) The safe limit of loudness of audible sound is
1. 0 to 80 dB
2. above 80 dB
3. 120 dB
4. above 120 dB
Answer: The correct answer is 1. 0 to 80 dB
(d) The unit of loudness is
1. cm
2. second
3. hertz
4. decibel
Answer: The correct answer is 4. decibel
(e) In a piano, the pitch is decreased by
1. using a thicker string
2. increasing tension
3. reducing the length of string
4. striking it hard
Answer: The correct answer is 1. using a thicker string
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Selina Class 8 ICSE Solutions Physics : Chapter 7- Sound
Download PDF: Selina Class 8 ICSE Solutions Physics : Chapter 7- Sound PDF
Chapterwise Selina Publishers ICSE Solutions for Class 8 Physics :
- Chapter 1- Matter
- Chapter 2- Physical Quantities and Measurement
- Chapter 3- Force and Pressure
- Chapter 4- Energy
- Chapter 5- Light Energy
- Chapter 6- Heat Transfer
- Chapter 7- Sound
- Chapter 8- Electricity
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