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Law of refraction HTML5

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The angle of reflexion is equal to the angle of incidence for all wavelengths. The refraction angle depends on the indices n1 and n2 of the two media. This is Snell's law, also known as Descarte’s Law, or The Law of Refraction.

When light passes from one medium to another, some of this light is reflected while another part penetrates into the medium with a change in its direction.

These two phenomena are called the reflection and refraction of light.

  • The angle of reflection of a ray of light is equal to its angle of incidence.
  • The angle refraction depends on the refractive indices n1 and n2 of the two media.

Refraction helps explain why a partially immersed object in a liquid seems broken at the surface. This refraction phenomenon also explains why a fish's apparent position is distorted from its real position..

Click and drag the fish.

Drag the 'slider' to change the index.

Learning goals

  • Illustrate Snell's law of refraction.
  • Explain when total internal reflection occurs.


Learn more

Consider the example of the fisherman on the shore (index of air n1 = 1) observing a fish in water (n2 > n1). The simulation can show that the fish appears thinner and closer to the surface than…

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