Geometric Optics

In the following formulas:

p = object distance
q = image distance
R = radius of curvature of the mirror
h = object height
h' = image height

Spherical Mirror  1. p, q, f, R are positive if on reflecting side of mirror.
2. M positive Þ upright and virtual image

M negative Þ inverted and real image

Principal Rays

1. Draw ray from top of object parallel to the optical axis and is reflected back through a focal point.
2. Draw ray from top of object through center of curvature. Ray reflects back on itself.
3. Draw ray from top of object through focal point and on to mirror. After reflection it runs parallel to the optical axis.

Thin Lens   1. p is positive if the object is in front of the lens. (real object)
2. p is negative if the object is in back of the lens. (virtual object)
3. q is positive if the image is in back of the lens. (real image)
4. q is negative if the image is in front of the lens. (virtual image).

Principal Rays

1. Draw ray from top of object parallel to the optical axis, through the lens and then passing through a focal point.
2. Draw ray through center of lens. Path remains undeviated.
3. Draw ray through focal point and on to lens. After lens it runs parallel to the optical axis.