Early Years Science: Light

We experience light and shadow in our lives every day but often don't pay a great deal of attention to them. Providing opportunities for children to explore light and shadow builds on their natural curiosity and helps them to become more aware of the world around them.

What do I need to know?

Below is background information that you will to support young children's scientific learning. It is not intended that children in the Foundation Stage are taught these facts, but that you use them to provide experiences that the children can draw on as they build their own scientific understanding.

Light

Light is a form of radiation that is given out by a range of sources including the sun, the stars, electric and fluorescent light bulbs, fire and candles. Light from any of these sources travels in straight lines in all directions. Some of these light rays enter our eye directly and we 'see' the light source. When light falls on objects all around us, some is absorbed by the object, while the rest bounces off from its surface. Light bouncing from the surface of an object enters our eye and then we 'see' that object.

How we 'see' things

The pupil at the front of our eyes controls the amount of light that enters our eyeballs. In bright light the pupil contracts to leave only a small hole for light to pass through. In poor light the pupil expands to allow as much light in as possible. The light rays fall on the back of the eyeball, the retina, which is covered in nerve endings. These are stimulated by light entering the eye and transmit messages to the brain. These messages are translated in our brain to images which have shape, depth and colour - these are the objects we 'see'.

The moon and the stars

The moon is not a source of light. Instead, it reflects the light of the sun. As the moon orbits around Earth every month, it appears to change shape depending on where it is in its orbit. A full moon's light can be bright enough to cast pale shadows of opaque objects.

The stars are sources of light and appear tiny because they are so far away. The nearest star to us is the sun. It appears larger to us on Earth because it is closer than the other stars. We can see the other stars only at night because of the brightness of the sun during the day.

Transparent, translucent and opaque

• A transparent material allows almost all of the light falling on it to pass through. If you look through a transparent material you will be able to clearly see the shape, outline and colour of objects on the other side of it. Clear glass is an example of a transparent material.

• A translucent material allows some light to pass through, but reflects or absorbs the rest. If you look through a translucent material you will be able to see the vague shape of an object behind it, but will not be able to make out the detail. Greaseproof paper and frosted glass are good examples of translucent materials.

• An opaque material does not allow any light to pass through it. It either reflects or absorbs all of the light that falls on it. If a bright light is shone on an opaque material, it will cast a shadow on the surface behind it.

Shadows

An opaque object - let's take a cardboard box as an example - forms a shadow if a light is shone on it, because it blocks out the light that would fall on the surface behind it (let's use a wall an example).

If the box is close to the wall, and the light source is bright, the shadow will have very distinct, sharp edges and the shadow will be only slightly larger than the box.

As the box and the light source are moved away from the wall, the shadow gets bigger but the edges become fuzzy and less distinct. If the light source is tilted at an angle to the box, the shape of the shadow changes.

Shadows outdoors

When you go outside at different times on a sunny day, you will notice that shadows change shape and position. This is because of the rotation of our Earth around the sun.

Early in the morning the sun appears in the east, low in the sky. Shadows formed at this time will be long and thin. As the Earth rotates, the sun appears to rise in the sky, until at midday it is directly above us.

Shadows cast at this time of day will be short and fat, and may hardly exist at all.

During the afternoon the sun appears to sink in the sky towards the west.

By late afternoon, shadows will be long and thin again, but will be pointing in the opposite direction to where they were in the morning.

Investigating

What colour is green?

What you need

A collection of leaves from plants, shrubs and bushes around your setting; shade cards or colour charts for paint; coloured acetate sheets; colour paddles; lightbox or a bright, clean window What to do

• Help the children to lay the leaves out on the surface of the lightbox. (Alternatively, they could lay them out on a plain, light-coloured surface next to a window.)

• Look carefully together at each of the leaves and ask the children to describe what they can see, and help them to notice the different shades of colour there are. How many different shades of green can you see? Can you think of names for all green colours?

• Try matching some of the leaf colours with the shades on the colour chart.

• Encourage the children to look at the leaves through each of the coloured acetate sheets. What can you see now? Have the colours changed?

• Encourage the children to go on investigating the leaves on the lightbox. Discuss their shape, size and texture as well as colour.

• Note down the comments that the children make while they are involved in their investigations.

• Make a lightbox display of the leaves, accompanied by the children's ideas and discoveries. Use this to prompt the investigation of other materials - transparent, translucent and opaque.

Shadow dance

What you need

A sunny day; outdoor area where children will be able to see their shadows easily What to do

• Draw the children's attention to the shadows on the ground and discuss their shape, size and colour.

• Encourage the children to investigate all the shadow shapes they can make with their bodies - to move their arms around, sit down, stand up. What happens to your shadow? Who can make the tallest shadow? Who can make the smallest shadow?

• Talk about where your shadow seems to join your body. What happens when you stand on one leg, hop or jump in the air? Can you make your shadow disappear?

• If possible, repeat this whole activity with the same group of children in the same place at a different time of day. What do you notice about the shadows now?

Linda Thornton and Pat Brunton are education consultants with a special interest in science and technology for young children. They can be contacted at www.alcassociates. co.uk