Physics · Chapter 05
🔦 Light & Reflection
Mirrors, lenses, rainbows.
💡 The Law of Reflection
When light hits a smooth surface (like a mirror), it bounces off. The rule is simple:
Angle of incidence = Angle of reflection
Both angles are measured from a line drawn perpendicular to the surface (called the normal). Hit a mirror at 30° → light reflects at 30°.
This is why you can see yourself in a mirror — light from your face hits it and bounces back to your eyes. Lenses bend light differently to focus it (your eye, a camera, a magnifying glass).
Light dispersion through prism — white light splits into spectrumWikimedia Commons / CC BY-SA 3.0
Rainbow — natural dispersion of sunlight by water dropletsWikimedia Commons / CC BY-SA 3.0
🎬
Bouncing Light Ray
AnimationA light ray strikes the mirror and bounces off at exactly the same angle. Watch the photon travel.
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Change the Angle
ExperimentAdjust the angle of incidence. The reflected ray always matches it.
37°
Angle of incidence37°
Angle of reflection37°
Both angles are measured from the normal (the perpendicular line). They are always equal.