A mirror changes the direction of a ray by reversing the component of its direction perpendicular to the surface. The component along the surface remains unchanged. This produces equal angles from the normal. When a plane mirror rotates while the incoming direction stays fixed, the reflected direction changes by twice that rotation.
Light, sound and electricity · Discover & try
How can a mirror redirect light?
Reading level 4 of 5 · FluentChange
Word help
normal
A line perpendicular to a surface.
reflection
Light returning from a surface.
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One ideal plane mirror; ray directions are geometric and no laser is needed.
What to look for
- Angles use the perpendicular normal
- The incident ray remains fixed
- Turning the mirror redirects the reflected ray
Explain what you noticed
A ray meets a flat mirror at 25° from the normal. What is its reflected angle from the normal?
Keep this idea: Compare both ray angles with the normal.
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Source material checked 2026-10-28. Explanations and activities by Nepedia. Source links do not imply endorsement.
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