# NCERT Solutions for Class 8 Science Science - NCERT Solution Chapter 13

## Sound Class 8

### Exercise : Solutions of Questions on Page Number : 168

Q1 :

Sound can travel through

(a) gases only (b) solids only

(c) liquids only (d) solids, liquids and gases.

(d) Sound can travel through solids, liquids, and gases.

Sound requires a medium to travel through. Solid, liquid and gas provide the medium for sound. Hence, sound can travel through solids, liquids and gases.

Q2 :

Which of the following voices is likely to have minimum frequency?

(a) Baby girl (b) Baby boy

(c) A man (d) A woman

(c) A man

The voice of an adult man is of lower pitch in comparison to the voices of a baby boy, a baby girl and a woman. Since frequency of a sound is directly proportional to its pitch, man's voice is of minimum frequency in comparison to a boy, a girl, or a woman's voice.

Q3 :

In the following statements, tick 'T' against those which are true, and 'F' against those which are false.

(a) Sound cannot travel in vacuum. (T / F)

(b) The number of oscillations per second of a vibrating object is called its time period. (T / F)

(c) If the amplitude of vibration is large, sound is feeble. (T / F)

(d) For human ears, the audible range is 20 Hz to 20,000 Hz. (T / F)

(e) The lower the frequency of vibration, the higher is the pitch. (T / F)

(f) Unwanted or unpleasant sound is termed as music. (T / F)

(g) Noise pollution may cause partial hearing impairment. (T/F)

Q4 :

Fill in the blanks with suitable words.

(a) Time taken by an object to complete one oscillation is called _________.

(b) Loudness is determined by the________ of vibration.

(c) The unit of frequency is _________.

(d) Unwanted sound is called _________.

(e) Shrillness of a sound is determined by the _________of vibration.

Q5 :

A pendulum oscillates 40 times in 4 seconds. Find its time period and frequency.

Q6 :

The sound from a mosquito is produced when it vibrates its wings at an average rate of 500 vibrations per second. What is the time period of the vibration?

Q7 :

Identify the part which vibrates to produce sound in the following instruments.

(a) Dholak (b) Sitar (c) Flute

Q8 :

What is the difference between noise and music? Can music become noise sometimes?

Q9 :

List sources of noise pollution in your surroundings.

Q10 :

Explain in what way noise pollution is harmful to humans.

Q11 :

Q12 :

Sketch larynx and explain its function in your own words.