Mirrors reflect light because a thin metal coating bounces most incoming rays straight back.

The longer version

Polished metal reflects because its electrons are free to slosh back and forth, re-radiating most of the incoming wave instead of absorbing it. A household mirror puts a thin layer of silver or aluminium on the back of glass, so light passes through the glass, bounces off the metal, and passes back out.

Silver reflects slightly better across the visible range than aluminium does, but it tarnishes, so glass protects it. A mirror loses a small fraction of the light at each surface, which is why repeated reflections grow dim. Ancient mirrors were polished bronze or obsidian, far duller than modern glass.

Where this entry sits

These facts explore how light behaves and how human eyes turn it into the colors we see. Along the way you meet rainbows, prisms, mirrors, shadows, lasers, and optical tricks that fool our vision every day. The full list sits on the Color and Light page, where every entry is listed in order.

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More From Color and Light

Eight more entries

A red apple looks red because its skin absorbs most colors and reflects red wavelengths.

White objects look white because they reflect nearly all wavelengths of visible light equally.

Black surfaces look dark because they absorb most of the visible light that falls on them.

Sunlight contains all the colors of the visible spectrum blended together into white light.

Violet light has the shortest wavelength visible to humans, while red has the longest.

The sky looks blue because air molecules scatter short blue wavelengths more than long red ones.

Sunsets often look red because sunlight travels through more air, which scatters away the blue light.

Laser light differs from ordinary light because its waves are aligned and share a single wavelength.

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