World 1 · Reflection & Refraction · 7 minThe Law of Reflection
Angle in equals angle out
Teaching this? Open projector mode
When a ray hits a smooth surface it reflects. Measure angles from the normal — the line perpendicular to the surface at the point of contact.
The rule is exact: θᵢ = θᵣ. The incoming ray, the reflected ray, and the normal all lie in the same plane.
Check yourself
A ray hits a mirror at 30° from the normal. It leaves at…
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