Refraction occurs when light crosses between materials with different refractive indices. The index describes light's speed relative to its speed in vacuum. Snell's law connects the indices and the angles from the normal. A ray along the normal remains straight even though its speed and wavelength can change at the boundary.
Light, sound and electricity · Discover & try
Why does light bend at a boundary?
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refraction
A change in light direction across a material boundary.
refractive index
A ratio describing light speed in a material.
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See how it works
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Flat air-to-material interface using approximate visible-light indices; reflected light is omitted.
What to look for
- The normal stays fixed
- Glass and water bend differently
- Straight entry has no sideways bend
Explain what you noticed
A ray enters glass from air at 50° from the normal. How does its transmitted angle compare?
Keep this idea: Compare direction with the normal while holding the incoming angle fixed.
Follow the sources
- OpenStax / Rice University — The Law of Refraction
- NASA / Smithsonian Chandra — Somewhere Over the Rainbow
Source material checked 2026-10-28. Explanations and activities by Nepedia. Source links do not imply endorsement.
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