Light and Shadows

Where does light come from?

Light comes from a light source. A light source makes its own light. The biggest one is the Sun. Other light sources are lamps, torches, candles, and even some animals like fireflies.

Some things look bright but are not light sources. A mirror and the Moon do not make light — they only bounce light from somewhere else. That bouncing is called reflection.

Light travels in straight lines

Here is a big idea: light always travels in straight lines.

Because of this, light cannot bend around a corner. If something gets in the way, the light stops. That is how a shadow is made.

Why do shadows form?

A shadow appears when an object blocks the light. The light cannot pass through, so a dark shape lands on the wall or ground behind it.

How much light passes through depends on the material:

• Opaque — blocks all light. A book, a tree, you! These make dark, clear shadows.
• Translucent — lets some light through. Frosted glass or thin paper. These make faint shadows.
• Transparent — lets nearly all light through. Clear glass and water. These make almost no shadow.

Shadows change size and shape

Your shadow is not always the same. Move the light, and the shadow moves too.

• When the Sun is high at noon, your shadow is short.
• When the Sun is low in the morning or evening, your shadow is long.
• Move closer to a lamp and your shadow grows bigger on the wall.

A sundial uses this. The shadow of a stick moves all day as the Sun crosses the sky, and people can read the time from it.

Try it yourself! 🧪

You need a torch, a small toy, and a white wall in a dark room.

1. Shine the torch at the toy so a shadow lands on the wall.
2. Move the torch closer to the toy. The shadow gets bigger.
3. Move the torch far away. The shadow gets smaller and sharper.
4. Try a glass of water in front of the torch — barely a shadow, because water is transparent!

You just proved that light travels straight and that opaque things block it.

Light is a kind of energy. To learn how energy moves and changes, visit the many forms of energy.