Maharashtra Board Class 6 Science Chapter 14 Light and the Formation of Shadows PDF Download

Light And The Formation Of Shadows

Can You Tell?

1. Can we see anything in total darkness?

2. What helps us to see the objects around us?

3. What does the light in each one of the pictures originate from?

The objects or materials which emit light, meaning those which themselves are a source of light, are called luminous objects or materials.

The intensity of light is determined by the extent to which the objects emit light. For example, the light emitted by an electric torch is more intense than that obtained from a candle.

The objects or materials that are not sources of light themselves, are called non-luminous objects or materials.

Some man-made objects or materials also emit light. These are called artificial sources of light.

The Sun is the main natural source of light. Other stars seen in the night sky, fireflies, some anglerfish as well as honey mushroom are natural sources of light.

Teacher's Note

Light is very important for us to see things. Just like we cannot see anything in a dark room without a light, we also need light from the sun to see things outside.

Exam Trick

Remember: Things that make light = luminous (like sun, bulb, candle). Things that don't make light = non-luminous (like book, table, you).

Points to Remember

Luminous objects give out light.
Non-luminous objects do not give out light.
Natural sources of light are sun, stars, and fireflies.
Artificial sources of light are bulbs, candles, and lanterns.
Light intensity means how bright the light is.

The Propagation Of Light

You may have seen in the afternoon, rays of light entering through a slit in a door or a small hole in the roof. As these rays of light from the slit or the hole move towards the floor, the dust particles in their way are seen clearly. Due to these particles, the path of the light becomes visible and we can see that their path is along straight lines.

Let's Try This

Take three cardboards. Make a small hole in the centre of each cardboard using a thick needle. Arrange the cardboards in such a way that the three holes are in the same line. Stand a burning candle on one side of the cardboards and look at the flame of the candle from the other side.

Teacher's Note

Light always travels in straight lines. You can see this when sunlight comes through a window and you can see the path in the dust.

Exam Trick

Remember: Light travels straight like an arrow. It does not bend or curve by itself. This is called linear propagation.

Points to Remember

Light travels in straight lines.
This is called linear propagation of light.
You can see the path of light when dust particles are present.
Light rays move forward without bending.
Shadows are formed because light travels in straight lines.

Reflection Of Light

How Do We See An Object?

The rays of light falling on an object from a source of light are thrown back from the surface of that object. This is called reflection of light. We see the object when the reflected rays reach our eyes.

Stars are luminous. Planets, satellites are non-luminous. Sunlight reflected from the surface of the moon reaches us. That is how we can see the moon. We call this light moonlight.

Light travels in a straight line. This is called the linear propagation of light.

Let's Try This

Take a straight tube that can be bent easily. As shown in the figure, place a burning candle on a stand, and look at it through the tube. Then bend the tube and look at the candle again. What do you see?

Teacher's Note

Reflection means light bouncing back from something. When you look in a mirror, light from your face bounces back to your eyes. That is why you can see yourself.

Exam Trick

Remember: Reflection = light bouncing back. Like a ball bouncing off a wall. Mirror shows reflection. You see things because light reflects into your eyes.

Points to Remember

Reflection is when light bounces back from a surface.
We see objects because of reflected light.
Mirrors reflect light very well.
The moon is seen because of reflected sunlight.
Moonlight is just reflected sunlight from the moon.

Images In A Plane Mirror

Stand in front of a plane mirror and look at your image in it.

1. Raise your right hand. Which hand of the mirror image is raised?

2. What change do you see in the image if you decrease or increase your distance from the mirror?

3. Is there any difference between your height and height of the mirror image?

The left and right sides of the original object appear to be exchanged in the mirror image.

The image is as far behind the mirror as the object is in front of it.

The size of the image is the same as that of the object.

Teacher's Note

When you look in a mirror, your image looks the same size as you. But your left side looks like the right side and your right side looks like the left side in the mirror.

Exam Trick

Remember: In a plane mirror, left becomes right and right becomes left. Your image is same size. It is as far behind the mirror as you are in front of it.

Points to Remember

The mirror image swaps left and right sides.
The image size is same as the object size.
The image is upright in a plane mirror.
The image appears to be behind the mirror.
The distance from mirror equals the distance of image behind mirror.

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