Refraction & Lenses

Refraction is what happens when light changes direction as it moves between different materials. When light travels from air into glass (less dense to more dense), it bends towards the normal - that's the imaginary line perpendicular to the surface. Think of how a straw looks bent in a glass of water!

The opposite happens when light goes from water to air (more dense to less dense) - it bends away from the normal. This is why swimming pools always look shallower than they actually are.

Lenses use refraction to focus or spread light rays. The magnification factor tells you how much bigger or smaller an image appears compared to the original object: Magnification Factor = Image Size ÷ Object Size.

Convex lenses are thicker in the middle and focus light rays towards a focal point. They create images that are bigger than the original object and appear on the opposite side of the lens - perfect for telescopes and magnifying glasses.

Concave lenses work the opposite way - they're thinner in the middle and spread light rays away from a focal point. These create smaller images on the same side as the object, which is why they're used in torches to spread light out widely.

Quick Tip: Remember "CONvex CONcentrates" light rays together, while "CONCave sCatters" them apart!