The straight-out line is called the normal. We measure the incoming and reflected angles from this line, not along the mirror. Those two angles are equal for a flat mirror. Try a small turn of the surface and notice that the reflected ray turns more than the mirror does.
Light, sound and electricity · Discover & try
How can a mirror redirect light?
Reading level 2 of 5 · DevelopingChange
Word help
normal
A line perpendicular to a surface.
reflection
Light returning from a surface.
Watch · Try · Explain
See how it works
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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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