Physics·Properties of waves · NSSCO 4.3.3
Refraction of light
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Light doesn't always travel straight — when it crosses from air into water or glass it BENDS. This lesson builds the idea from scratch: why light bends (its speed changes), which way it bends (toward the normal going in, away coming out), the refractive index n = sin i / sin r with worked calculations, and the beautiful effect of total internal reflection and its critical angle that carries the internet through optical fibres.
What you'll learn in this lesson
By the end you should be able to (NSSCO Physics 4.3.3):
- Define refraction of light as the change in direction of light entering or leaving a medium of different optical density
- Explain that light refracts because its speed changes at the boundary between two media
- Draw and describe the refraction of a ray through a rectangular glass block — bending toward the normal on entering, away from the normal on leaving
- Recall and use the equation refractive index n = sin i / sin r in calculations
- Recall and use the definition of refractive index in terms of the speed of light
- Give the meaning of the critical angle and describe internal and total internal reflection
- Describe applications of total internal reflection, including optical fibres and prisms
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