Shadow formation and changes

In a nutshell

Shadows are formed when an opaque object blocks light. An opaque object is one which blocks all light from passing through. Light interacts with objects in different ways depending on which material they are made from. Shadows are dark shapes formed where there is no light present.

Objects and materials

The amount of light an object will let through depends on the material it is made from. There are three different types:

Science; Light; KS2 Year 3; Shadow formation and changes

	material type	description	can you see through?	Example
A	Transparent	Allows all or almost all light to pass through it.	Yes	Glass, water, air.
B	Translucent	Allows some light to pass through it.	No	Tissue paper, frosted glass, many fabrics.
C	Opaque	Blocks all light from passing through it.	No	Wood, stone, metal.

If an object is made of a material which is opaque, then it will create shadow. This is because it blocks all light from passing through it.

What is a shadow?

Shadows are dark shapes formed where there is no light present. They are formed when an opaque object blocks light from a source. Most shadows will normally have a similar shape to the object that created it.

Curiosity: You can make your own shadows at home! Put different objects in front of a lamp, and see the different shapes you can make!

The size of shadows can change depending on the time of day, if the Sun is causing the shadow. When the Sun is high (during the middle of the day), shadows are short. When the Sun is low (near the start and end of the day), shadows are long.

Science; Light; KS2 Year 3; Shadow formation and changes