Light, Shadows and Reflections

🔦 Imagine you are in a dark room and you switch on a torch. A bright beam shoots across the room and lights up the wall — but if you hold your hand in front of the torch, a dark shape appears on the wall behind it. That dark shape is a shadow! In this lesson we are going to find out exactly why shadows form and how light behaves when it meets different materials.

Light always travels in straight lines away from its source. A light source is anything that makes its own light, such as the Sun, a candle, or a torch. Because light cannot bend around corners by itself, it travels outward in straight lines called rays. Think of it like throwing lots of tiny balls in every direction from a single point — each ball travels in a perfectly straight path.

A shadow forms when an object blocks light rays. If an object gets in the way of those straight rays, the light cannot pass through it. On the other side of the object, where no light reaches, a dark area appears — the shadow. The shadow has a similar shape to the object because the straight rays of light cannot bend around its edges to fill the dark gap.

The size of a shadow changes depending on where the light source is placed. When the light source is very close to an object, the shadow is large. Move the light source further away and the shadow shrinks. This is because light rays spread out from their source. Up close, a wider spread of rays is blocked, creating a bigger shadow. From far away, fewer rays are blocked, so the shadow is smaller.

The angle of the light also changes the shadow's shape. If you shine a torch straight at an object from directly in front, the shadow looks like the object's outline. But if you tilt the torch to the side or shine it from a low angle, the shadow stretches and looks much longer and thinner. This is why your shadow in the morning or evening looks very long but at midday it is short and sits right beneath you.