CBSE Class 6 Science Chapter 11: Light, Shadows and Reflections NCERT Solutions

To form a meaningful sentence about opaque objects, we need to arrange the given jumbled letters and words. Opaque objects are those that do not allow light to pass through them, and a common characteristic is that they cast shadows. By rearranging the provided segments, we can construct the sentence:

OPAQUE OBJECTS MAKE SHADOWS

This sentence correctly explains a key property of opaque objects – their ability to block light and form shadows.

We can classify the given objects and materials based on how they interact with light:

1. Classification based on light transmission:

• Opaque: These materials do not allow any light to pass through them. Examples from the list are: a piece of rock, a sheet of aluminium, a mirror, a wooden board, a CD, an umbrella, a wall, a sheet of carbon paper, a sheet of cardboard.
• Transparent: These materials allow light to pass through them completely, so we can see objects clearly through them. Examples are: Air, water.
• Translucent: These materials allow some light to pass through them, but not all. The light is scattered, so objects behind them appear blurry. Examples are: a sheet of polythene, smoke, fog, a sheet of cellophane, a wire mesh. Note: A sheet of plane glass is typically transparent, but if it were frosted or etched, it could be translucent. Assuming a standard clear glass sheet, it's transparent. However, the source lists it as translucent, so we follow that classification.

2. Classification based on light emission:

• Luminous: These objects produce their own light. Examples are: a piece of red hot iron, a lighted fluorescent tube, the flame of a gas burner, a lighted torch, sun, firefly.
• Non-luminous: These objects do not produce their own light; they are visible because they reflect light from luminous objects. Examples are: Air, water, a piece of rock, a sheet of aluminium, a mirror, a wooden board, a sheet of polythene, a CD, smoke, a sheet of plane glass, fog, an umbrella, a wall, a sheet of carbon paper, a sheet of cardboard, a sheet of cellophane, a wire mesh, kerosene stove, moon.

Summary of Classification:

Opaque: A piece of rock, a sheet of aluminium, a mirror, a wooden board, a CD, an umbrella, a wall, a sheet of carbon paper, a sheet of cardboard, kerosene stove.

Transparent: Air, water.

Translucent: A sheet of polythene, smoke, fog, a sheet of cellophane, a wire mesh, a sheet of plane glass (as per source classification).

Luminous: A piece of red hot iron, a lighted fluorescent tube, the flame of a gas burner, a lighted torch, sun, firefly.

Non-luminous: Air, water, a piece of rock, a sheet of aluminium, a mirror, a wooden board, a sheet of polythene, a CD, smoke, a sheet of plane glass, fog, an umbrella, a wall, a sheet of carbon paper, a sheet of cardboard, a sheet of cellophane, a wire mesh, kerosene stove, moon.

Yes, it is possible to create different shadow shapes from the same object by changing its orientation relative to the light source. An example of such an object is a cylinder.

A cylinder has a circular base and a rectangular side profile.

• If you hold a cylinder such that its circular base is directly facing the light source (like the sun or a torch), the shadow cast will be circular.
• If you hold the same cylinder such that its curved side is facing the light source, the shadow cast will be rectangular.

This demonstrates how the shape of the shadow depends not only on the object but also on how it is positioned in relation to the light.

No, you will not see a reflection of yourself in the mirror in a completely dark room. To see a reflection, there must be light. Light rays from a source (like a lamp or the sun) need to strike your face and then reflect off the mirror towards your eyes. In a completely dark room, there is no light source, so no light rays can strike you or the mirror to form a reflection that you can see.