Essential Equations

Question 1

Object/image locations

Answer 1

ℓ = n1/L
ℓ’ = n2/L’

Location = index of refraction/vergence

Question 2

Power of a mirror

Answer 2

F = -2n/r

*must remember C is positive, Ↄ is negative

Question 3

Lens-mirror combo

Answer 3

F = 2F1 + F2

Power = 2*front surf + power of mirror

Question 4

Spherical equivalent

Answer 4

Fse = Fcyl/2 + Fsphere

Question 5

General vergence

Answer 5

L’ = F + L

Image vergence = power + object vergence

Question 6

Effective/downstream vergence

Answer 6

Leff = L/(1-dL)

Effect verg = (verg at r=0)/(1-(distance)(verg at r=0))

Question 7

Power of an SSRI

Answer 7

F = (n2-n1)/r

Power = diff in indices/radius of curvature (meters)

Question 8

Equivalent power

Answer 8

Fe = F1 + F2 - ((t/n2)F1F2)

Equiv power = front surf + back surf - ((thickness(m)/n2)(front surf)(back surf))

Question 9

Back vertex power

Answer 9

Fv = F2 + (F1/(1-(t/n2)(F1))

BVP = back surf + (front surf/(1-(thickness/n2)(front surf))

Question 10

Lateral magnification

Answer 10

m = hi/ho = L/L’ = ℓ’/ℓ

= height image/height object
= object verg/image verg
= image location/object location (only if both are in same index of refr)

Question 11

Vertex distance

Answer 11

Fc = Fg/(1-(d)(Fg))

Power contact lens = (power glasses)/(1-(distance)(power glasses))