N¹ sin(θ¹) = N² sin(θ²)

N = index of refraction

θ = angle between ray and normal

N= C / V

N = index of refraction

C = speed of light

V = speed of stuff thru material

*The higher the speed the lower the index of refraction*

1/dº + 1/d¹ = 1/f

d° = object distance

d¹ = image distance

f = focal length

m = (-d¹ / d°) = (h¹ / h°)

m = magnification

d/h ¹ = image distance/ height

d/h ° = object distance/height

f = R / 2

f = focus 

r= center of curvature 

a positive image distance

a negative image height

a positive object distance

a positive object height

a negative magnification

a positive magnification

a negative image distance

a positive image height

a positive object distance and height