Selina solutions for Concise Physics [English] Class 8 ICSE chapter 7 - Sound [Latest edition]

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

In a longitudinal wave, compression and rarefaction are formed.

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

The frequency is measured in second.

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

The pitch of sound depends on frequency.

Decibel is the unit of pitch of a sound.

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

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

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

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

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

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

Match the following

Sound can not travel in

When sound travels in form of a wave

The safe limit of loudness of audible sound is

The unit of loudness is _______.

In a piano, pitch is decreased by

How does sound travel in air?

What is longitudinal wave?

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

Which of the following determines the loudness of a sound wave?

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 that of 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 of high pitch note and a low pitch note, but of the same loudness.

Standing at a distance, how is it possible to detect the filling of bucket under a water tap by hearing the sound? 

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 loudness and pitch. Will they differ in quality? 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) waveform (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?

Two waves of the same pitch have amplitudes in the ratio 1 : 3 What will be the ratio of their

1. loudness,
2. pitch?

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

Two waves have the same pitch but their amplitudes are in the ratio of 1 : 2. Draw a figure to show the two waves.

Two waves of the same amplitude have frequencies 256 Hz and 512 Hz respectively. Represent the two waves in the graphical form.