Explore Shadows and Their Shapes

Shadows - they're everywhere! But why do they happen?

Shadows are formed when light waves reach an object they cannot pass through.

Light waves travel in straight lines called rays or waves.

When they reach an opaque object, the light waves that hit it, bounce back and cannot pass through - this is part of how we see things.

Then the light rays that can pass around it, continue travelling until they hit the surface behind - they continue passing in a straight line.

This is how shadow puppets work.

Using a strong light, such as a lamp or torch and our hands, we can block the light in different shapes.

The light that passes illuminates the surface around our hands - it continues travelling until it hits a surface.

The light that is blocked forms a dark area behind our hands, creating a shadow in whatever shape it may be.

Shadows are always the same shape as the object that is blocking them.

Like this person, for instance - the shadow is the shape of a person because the light source is directly in front of them.

You may notice that sometimes shadows appear longer or shorter at different times of day. This is true of shadows created by the Sun.

Because the Sun rises in the east and sets in the west, shadows outdoors are longer earlier in the morning and later in the afternoon. The lower the angle of a light source, the longer the shadow will appear.

When the Sun is high above us at midday, shadows appear shorter and directly behind or underneath objects - like us!

So, just remember:

-  Shadows are created when a light source shines on an opaque or translucent object (opaque objects make darker shadows).

-  A shadow is an absence of light (darkness)

-  Shadows can be different lengths, depending on the angle of light, or different sizes - larger or smaller, if the light is closer or further away.

-  Shadows are the same shape as the object they are behind.

Are you ready to try some questions?