# 45. Basic Concepts of Geometrical Optics

version from 2016-02-04 21:44

## Section

1: Light is an electromagnetic wave.
2. The speed of light is 3.0 x 10^8 m/s IN A VACUUM
3. Light has a dualistic nature, that is it can be represented as both a wave and as a particle
4. Light travels at slower speeds through more optically dense mediums. This slower speed is the

## Absolute Refractive Index

nAbsoluter Refractive Index
cSpeed of light in a Vacuume
vSpeed of light in the other medium

The refractive index is how many time slower light travels through a medium, compared to a vacuum

## Important Laws for you to know

Law of ReflectionThe angle of incidence is equal to the angle of reflection
Law of RefractionLight that will travel from an optically denser medium to an optically less dense medium will bend away from the normal.
Total Internal RefractionComplete reflection of a beam of light, resulting in its propagation down, say, a light-conducting fibre.

## Snells Law:

aangle of incidence
bangle of refraction
v1 or 2speeds of light in the media
n2 or 1Absolute refractive indexes of 2 media

## Lens Equation

1/f = 1/a + 1/b

aobject distance
ffocal length
bimage distance

5. Mirrors can be Plane, Convex or Concave
6. Sometimes, 2 waves interfere with eachother. This may amplify or attenuate the wave. This is INTERFERENCE.
7. To create a Stable interference Image of Light, it must have:
a) Monofrequency light (all light of same frequency)
b) Polarized light (light in a single plane)
c) Coherent: Have a permanent phase difference that doesnt change over time
8. When a beam of light passed through a small opening, itcan be dispersed, and create an interference pattern. This is DIFFRACTION.
9. As light waves can oscillate in multiple directions, they can have the direction specified, so that the light all goes the same way. This is POLARISATION.