Q3 of 18 Page 165

Identify the mistakes and correct them:

Unwanted sound from any loudspeaker that causes discomfort of any kind is called Music.

Unwanted sound that causes discomfort is called Noise Pollution. Too much noise can damage the human ear, and cause other health problems.

Music refers to the sound which pleases a person. It does not cause any discomfort.


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2

Fill in the blanks:

1. The working principle of a periscope is __________________


2. A fruit appears to be bigger in a glass of water due to _____________


3. Sound cannot travel in ___________


4. When we touch the ringing bell we can feel the ______________


5. An audible sound has the frequency range of _____________

 3

Identify the mistakes and correct them:

The beautiful pattern that we obtain in a kaleidoscope is because of refraction.

 3

Identify the mistakes and correct them:

An optical fibre is a device based on the principle of refraction.

 4

Match the following:

a. Irregular reflection - Glass slab


b. Multiple reflection - Optic fibre


c. Refraction - Periscope


d. Total internal reflection – Wood