Grade 5 · Unit 4: The way we see things

Which surfaces reflect light best?

Shiny and smooth, or dull and rough?

Even a rough brick wall reflects some light – that is how we see it.

All surfaces reflect

Almost all surfaces reflect some light. That is how we see them. But some surfaces reflect light much better than others. Shiny, smooth surfaces reflect light well. Dull, rough surfaces reflect less.

Light colours reflect more light than dark colours, so white houses stay cooler in hot countries.

Smooth and rough

A smooth surface reflects light in one direction, so it looks shiny. A rough surface scatters light in many directions, so it looks dull. Light colours reflect more light than dark colours.

Polished floors and still water can be so smooth that they reflect a clear image, just like a mirror.

Testing surfaces

Shine a torch at different surfaces and measure the reflected light with a light meter. Keep the torch, distance and angle the same. Foil and white paper reflect much more than black cloth.

Light meters are used by photographers to choose the right camera settings, and by architects to check rooms get enough daylight.

Reflecting to stay safe

Reflective strips on bags, clothes and rickshaws bounce car headlights back. Road signs and cat’s eyes in roads reflect light too.

Road signs use tiny glass beads or prisms that send light straight back towards the car that lit them.

What I learnt