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Selina solutions for Class 8 Physics chapter 7 - Sound

Selina Concise Physics - Middle School for Class 8 (2018-19 Session)

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Selina Selina Concise Physics - Middle School Class 8 (2018-19 Session)

Selina Concise Physics - Middle School for Class 8 (2018-19 Session)

Chapter 7: Sound

Chapter 7: Sound solutions [Page 0]

Write true or false 

When sound propagates in air, it does not carry energy with it.

Write true or false 

In a longitudinal wave, compression and rarefaction are formed.

 Write true or false 

The distance from one compression to nearest rarefaction is called wavelength.

Write true or false 

The frequency is measured in second.

Write true or false 

The quality of a sound depends on the amplitude of wave.

 Write true or false 

The pitch of sound depends on frequency.

Write true or false 

Decibel is the unit of pitch of a sound.

 Fill in the blank

The time period of a wave is 2 s. Its frequency is..........

 Fill in the blank 

The pitch of a stringed instrument is increased by .................. tension in string.

 Fill in the blank

The pitch of a flute is decreased by ................... length of air column.

 Fill in the blank

Smaller the membrane, ..................is the pitch.

 Fill in the blank

 If a drum is beaten hard, its loudness ................

 Fill in the blank

 A tuning fork produces sound of ...................frequency.

Match the following

        column A          column  B
(A) Amplitude  (1) frequency
(B) Frequancy  (2) amplitude 
(C) Loudness (3)maximum displacement           on either side 
(D) Pitch (4) presence of other  frequencies
(E) Wave form (5) 1/ time period

 Select the correct alternative

 Sound can not travel in

  1.  solid
  2.  liquid
  3.  gas
  4.  vacuum

Select the correct alternative

 When sound travels in form of a wave

  1. the particles of medium move from the source to the listener
  2.  the particles of 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.

Select the correct alternative

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

Select the correct alternative

The unit of loudness is

  1. cm
  2.  second
  3.  hertz
  4.  decibel

Select the correct alternative

In a piano, pitch is decreased by

  1.  using thicker string
  2.  increasing tension
  3.  reducing length of string
  4.  striking it hard Ans.

Chapter 7: Sound solutions [Page 0]

How does sound travel in air ?

What is longitudinal wave ?

Explain the mechanism of formation of a longitudinal wave
when source vibrates in air.

Define the following terms :
(a) Amplitude
(b) Frequency
(c) Time period.

Obtain relationship between the time period and frequency.

Name three characteristics of a musical sound.

Name the quantity from below which determines the loudness of a sound wave :
(a) Wavelength
(b) Frequency, and
(c) Amplitude

How is loudness related to the amplitude of wave ?

If the amplitude of a wave is doubled, what will be the effect on its loudness ?

How does the wave pattern of a loud note differ from a soft note ? Draw a diagram

Name the unit in which the loudness of sound is expressed.

Why is the loudness of sound heard by a plucked wire increased when mounted on a sound board ?

State three factors on which loudness of sound heard by a listener depends.

What determines the pitch of a sound ?

Name the characteristic of sound related to its frequency

Name and define the characteristic which enables one to distinguish two sounds of same loudness, but of different frequencies, given by the same instrument.

Draw a diagram to show the wave pattern ofhigh pitch note and a low pitch note, but of the same loudness.

How is it possible to detect the filling of a bucket under a water tap by hearing the sound standing at a distance ?

The frequencies of notes given by flute, guitar and trumpet are respectively 400 Hz, 200 Hz and 500 Hz. Which one of these has the highest pitch ?

Figure shows two jars A and B containing water up to different heights. Which will produce sound of higher pitch when air is blown on them ?

Two identical guitars are played by two persons to give notes of the same pitch. Will they differ in quantity ? Give reason for your answer.

Two musical notes of the same pitch and same loudness are played on two different instruments. Their wave patterns are as shown in figure.

How do they differ in
(a) loudness,
(b) pitch and
(c) quality

Which characteristics of sound makes it possible to recognize a person by his voice without seeing him ?

State the factors that determine
(a) the pitch of a note.
(b) the loudness of the sound heard.
(c) the quality of the note.

Name the characteristic of the sound affected due to a change in its

(a) amplitude (b) wave form (c) frequency.

Figure shows four waves A, B, C, and D

Name the wave which shows
(a)a note from a musical instrument,
(b)a soft note
(c) a shrill note.

How is the pitch of sound in a guitar changed if (a) thin wire is used, (b) wire under less tension is used ?

Chapter 7: Sound solutions [Page 0]

1. Two waves of the same pitch have amplitudes in the ratio 1: 3 What will be the ratio of their (i) loudness, (ii) pitch ?

Two waves have frequencies 256 Hz and 512 Hz, but same amplitude. Compare their (i) loudness, and (ii) pitch

Chapter 7: Sound

Selina Selina Concise Physics - Middle School Class 8 (2018-19 Session)

Selina Concise Physics - Middle School for Class 8 (2018-19 Session)

Selina solutions for Class 8 Physics chapter 7 - Sound

Selina solutions for Class 8 Physics chapter 7 (Sound) include all questions with solution and detail explanation. This will clear students doubts about any question and improve application skills while preparing for board exams. The detailed, step-by-step solutions will help you understand the concepts better and clear your confusions, if any. Shaalaa.com has the CISCE Selina Concise Physics - Middle School for Class 8 (2018-19 Session) solutions in a manner that help students grasp basic concepts better and faster.

Further, we at Shaalaa.com are providing such solutions so that students can prepare for written exams. Selina textbook solutions can be a core help for self-study and acts as a perfect self-help guidance for students.

Concepts covered in Class 8 Physics chapter 7 Sound are Concept of Pitch and Frequency, Pitch and Frequency in Relation to Working of Musical Instruments. (Wind, Membrane and String), Concept of Mono Tone, Concept of Loudness and Amplitude, Concept of Unit of Loudness in Decibels.

Using Selina Class 8 solutions Sound exercise by students are an easy way to prepare for the exams, as they involve solutions arranged chapter-wise also page wise. The questions involved in Selina Solutions are important questions that can be asked in the final exam. Maximum students of CISCE Class 8 prefer Selina Textbook Solutions to score more in exam.

Get the free view of chapter 7 Sound Class 8 extra questions for Physics and can use Shaalaa.com to keep it handy for your exam preparation

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