Refraction
Describe the refraction of light between two media.
- Refraction is the change in direction of a light ray as the ray passes from one medium into another.
- Refraction is a result of the speed of light changing when light enters a new medium.
- The index of refraction of a given medium is inversely proportional to the speed of light in the medium. Relevant equation:
- Snell’s law relates the angles of incidence and refraction of a light ray passing from one medium into another to the indices of refraction of the two media. Relevant equation:
- When a light ray travels from a medium with a higher index of refraction into a medium with a lower index of refraction, the ray refracts away from the normal.
- When a light ray travels from a medium with a lower index of refraction into a medium with a higher index of refraction, the ray refracts toward the normal.
- When a light ray is incident along the normal to a surface, the transmitted ray is not refracted.
- Total internal reflection may occur when light passes from one medium into another medium with a lower index of refraction.
- Total internal reflection of light occurs beyond a critical angle of incidence. Derived equation:
- For incident rays at the critical angle, the ray refracts at 90 degrees and travels along the surface of the material.
- For incident rays beyond the critical angle, all light is reflected (no light is transmitted into the other medium).