Geometric+Optics

= = Geometric Optics

Law of Reflection

 * A flat plane mirror reflects light at the same angle that is incident.
 * Whereas the angle to the normal that the light strikes at (Theta)i is equal to the reflected angle (Theta)r

Images
Below is a demonstration media type="custom" key="17524486"
 * Images are what are created due to reflected light. Images are either real or virtual
 * Virtual images are what you perceive (Like when you look into a mirror)
 * Real images are when you can see an image on a screen, in other words, light rays cross.

There are 3 steps to drawing any ray diagram.
 * 1) Draw the first ray parallel with the axis (This ray when parallel will always travel, after reflecting, back through the focal point)
 * 2) Draw the second ray through the focal point. (This ray when throught the focal point will always travel back parallel to the axis)
 * 3) Draw the 3rd perpendicular to the curvature of the mirror/lens. (This ray will always travel straight back through its original path)

Refraction
When light travels between two transparent mediums there is what is called refraction. The very basic equation is n = c/v where c = 3X10^8 m/s

Snell's law defines the refraction or bending of light when it makes that transition from one medium to another. This very basic analogy can be made of the marching band traveling from concrete to mud! As the marching band travels into the mud the band slows down on one side until the other can catch up causing the band to change direction in a slight manner. Light acts in the same way.

Snell's Equation is n1Sin(theta1) = n2Sin(theta2) where n1 is the index of refraction for the first medium and n2 for the second.

There comes a time when light hits a medium at such a steep angle along with the other medium having a high index of refraction that it becomes "Totally internally refracted." This light cannot escape the object it is trapped in. Modern technologies such as fiber optic cables use this today.

Thin Lenses
All equations above can be used for thin lenses. The only difference being that light actually travels through instead of completely reflecting.

To find out how much an image has been magnified by a lens you use the equation m = hi/ho = -di/do

To find how far an image or focal point is from the lens you use 1/d0 + 1/di = -1/f