## Thursday 15 December 2022

### CBSE Class 8 - Physics - Sound - Case Study Based Question #class8Science #Sound #Physics #eduvictors

CBSE Class 8 - Physics - Sound - Case Study Based Question

Sound is a form of energy that is produced when air molecules vibrate in a particular pattern called waves. Hence, the sound is a wave. Sound is produced by vibrating objects. Vibration can be described as to and fro motion of an objects. Sound cannot be produced without any vibrations. Sound always requires a medium to travel from the source of its production to the receiver end. Speed of the sound is maximum in solids and minimum in gases.

(i) The audible frequency range of a human ear is:

(a) The range of audible frequency of human ear is 20 to 200 Hz

(b) The range of audible frequency of human ear is 2 Hz to 20 Hz

(c)The range of audible frequency of human ear is 200 to 2000Hz.

(d) The range of audible frequency of human ear is 20 to 20,000Hz

(ii) Ria used a device to measure the loudness of a machine. She recorded her observation as given below. Which of the following represents the correct measurement of loudness?

(a) 80 Hz

(b) 80 s

(c) 80 dB

(d) 80 k

(iii) Arrange the speed of sounds in solids, liquids and gases in an ascending order:

(a) Gas < Liquid < Solid

(b) Liquid > Gas > Solid

(c) Liquid < Solid < Gas

(d) Solid > Liquid > Gas

(iv) The number of vibrations made by a vibrating body in one second is:

(a) frequency

(b) noise

(c) loudness

(d) pitch

1. (d) The range of audible frequency of human ear is 20 to 20,000Hz

2. (c) 80 dB

3. (a) Gas < Liquid < Solid

4. (a) frequency