Light reflects from surfaces — Physics, 7–10 years
Light can bounce from a surface into our eyes, allowing us to see objects and images. Smooth and rough surfaces reflect light in different ways.
Light bounces
We see an object when light from a source reaches it and some of that light enters our eyes. A smooth surface sends the light in an organised direction, which can make a clear image. A rough surface sends light in many directions, so we see the surface but not a sharp reflection.
Why this matters
People needed to explain how mirrors, still water and polished metal can show images, even though they do not make their own light. The useful idea is that light travels from a source to a surface and then towards an observer. This lets us predict where a reflection will appear instead of treating it as a mystery.
Seeing a lamp in a mirror
Put a lamp on the left side of a mirror and stand on the right. Light travels from the lamp to the mirror. The mirror reflects some of it towards your eyes, so you see the lamp’s image behind the mirror. If you move to the left, the reflected light no longer travels into your eyes, and the image seems to disappear.
The reflection mistake
A reasonable mistake is thinking that a mirror makes a copy of an object or sends all light straight back. A mirror only redirects some of the light that reaches it, and the image is formed because the reflected rays enter our eyes in a particular way. A rough wall reflects light too, but scatters it instead of making a clear image.
Where it appears
Mirrors help drivers see behind them, let dentists see difficult places and guide light in some instruments. Reflective strips on bicycles and coats send car headlights back towards drivers, making people easier to notice at night. Calm lakes can show reflections because their surfaces are smooth enough.
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