Principle of Least Time
The path taken between two points by a ray of light is the path that can be traversed in the least time. Another name for the principle of least time is Fermat's principle.
Law of Reflection
- the angle of incidence equals the angle of reflection
- [math]\theta_i = \theta_r[/math]
Index of Refraction
|The index of refractive index of a medium is a measure of the reduction in the speed of light inside the medium in comparison to the speed in a vacuum. Also called refractive index.
Law of Refraction
- the index of refraction in medium 1 multiplied by the sine of the angle medium 1 equals the index of refraction in medium 2 multiplied by the sine of the angle in medium 2.
- [math]n_1 \sin(\theta_1) = n_2 \sin(\theta_2)[/math]
- light rays traveling in a high index medium bend away from the normal when refracting into a lower index medium
- light rays traveling in a low index medium bend towards the normal when refracting into a higher index medium
|The angle where refraction occurs at 90 °. Beyond the critical angle there is total internal reflection. The critical angle only exists for rays that are in a high index medium and encounter a boundary with a lower index medium.
the variation of the index of refraction with wavelength.
As a consequence rays with different wavelengths refract at different angles when traveling through a dispersive medium.