6th Class Science Lights, Sound and Force Introduction


Category : 6th Class

*       Introduction


Light is one of the important natural resources. Without light no life is possible on the earth. Sun is the source of light on Earth. We able to see the things because of the reflection of light. The object which produces light is called luminous object. And the objects, that do not produce light are, non-luminous object. Moon in the sky does not have its own light. It shines by the reflection of Sun light.

Light does not require any medium to travel. It can travel in the vacuum also. Depending upon the passing of light through the objects, they are divided into three groups;

(i) Transparent object: It allows light to pass through it, e.g. glass, water, etc.

(ii) Translucent object: It allows only certain amount of light to pass through it, and absorbs rest of light. For example, butter paper, etc.

(iii) Opaque: It does not allow light rays to pass through it, at all. For example, stone, wood, book etc.

Sound also plays an important role in our life. We are able to communicate with each other because of the sound energy. Sound waves require medium to travel. The atmosphere or air around the Earth provides the medium for the travel of sound waves. In this chapter, we will study about the properties of light and sound.

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