Classify the objects or materials given below as opaque, transparent or translucent, and luminous or non-luminous:
Air, water, a piece of rock, a sheet of aluminum, a mirror, a wooden board, a sheet of polythene, a CD, smoke, a sheet of plane glass, fog, a piece of red hot iron, an umbrella, a lighted fluorescent tube, a wall, a sheet of carbon paper, the flame of a gas burner, a sheet of cardboard, a lighted torch, a sheet of cellophane, a wire mesh, kerosene stove, sun, firefly, moon.

Before classifying the given objects or materials let us know the definition and examples of opaque, transparent or translucent, and luminous or non-luminous objects.

(1). Opaque Objects:

Those objects which do not allow light rays to pass through them are known as opaque.

Examples of opaque objects: 

Wooden board, walls, rubber, etc. are opaque objects.

(2). Transparent:

Those objects which allow light rays to pass through them in straight lines are known as transparent. As a result, we can see the objects clearly. 

Example of transparent objects: 

Air, water, and glass are transparent objects.

(3). Translucent:

Those objects which let some light pass through them, are known as translucent. In these types of objects, the light rays get scattered in all directions, so we cannot see clearly through them. 

Example:

Fog and smoke are translucent.

(4). Luminous:

Those objects emit light on their own. 

Example:

Sun and Firefly are luminous objects.

(5). Non-luminous:

Those objects which can't emit light on their own, but rather reflect the light from luminous bodies, are known as Non-luminous.

Example:

Moon and mirror are non-luminous objects.

Based on the above definitions the objects or material given can be classified as:

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Updated on: 10-Oct-2022

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