The reflective layer behind a household mirror
A typical household mirror uses a thin reflective metal coating behind a sheet of glass. Light passes through the glass, reflects from the coating and returns to your eyes. Because the reflective surface is smooth, it preserves the orderly directions of the light instead of scattering them like a painted wall.
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Smooth reflection preserves an image
Most ordinary household mirrors have a reflective metal layer behind glass, with protective coatings behind the metal. The glass supports and protects the delicate reflecting surface.
At a smooth reflective surface, incoming and outgoing light follow a regular relationship: the angle of reflection equals the angle of incidence. Light from different points on your face therefore reaches your eyes in an orderly pattern.
Your brain traces the reflected rays back as if they came from behind the mirror. For a flat mirror, the image appears as far behind the surface as the object is in front.
- Smooth reflection can form a clear image.
- A rough surface scatters light in many directions.
Some specialised mirrors place the reflective coating on the front to avoid the extra reflections produced by a glass layer.