1 - SSRI, Snell’s

Question 1

General vergence equation

Answer 1

L’ = P + L

Image vergence) = (power) + (object vergence

Question 2

4 equations that don’t use meters

Answer 2

Minimum blank size
Prisms
CLS power
Calc AC/A

Question 3

Object and image locations equations

Answer 3

ℓ = n1/L
(Object location) = (index before lens)/(object vergence)

ℓ’ = n2/L’
(Image location) = (index after lens)/(image vergence)

Question 4

Real object/image

Virtual object/image

Answer 4

RO: light diverges from (-verg)
RI: light converges to (+verg)

VO: light converges from (+verg) - we cannot make in space unless there’s a lens that created the image that become the virtual object
VI: light diverges to (-verg)

Question 5

Define concave/convex surfaces

Answer 5

Cave: interface wraps around lower n medium -> diverging

Vex: inferace wraps around higher n medium -> converging

Question 6

Power of an SSRI equation

Answer 6

P = (n2-n1)/r

(Power) = (n2-n1)/(radius of curvature (meters))

r is either positive or negative: + opens to right, - opens to left

Question 7

Secondary focal point/length definitions

Answer 7

SFP (F’): location of image point when light from infinity (plane-polarized) is incident on the interface

SFL (f’): distance from interface to F’
-this is the image location when the object is at ℓ = infinity

*key = parallel light INTO the lens

Question 8

Primary focal point/length definitions

Answer 8

PFP (F): location of the object point from which light can leave so that it exits as plane waves

PFL (f): distance from interface to F
-object location when the image is at ℓ’ = infinity

*key = parallel light OUT of lens

Question 9

Finding secondary focal point (f’) equation

Answer 9

f’ = n2/F

Question 10

Finding primary focal point (f) equation

Answer 10

f = n1/F

Question 11

If a lens is in air, the primary and secondary focal points are

Answer 11

The inverse of the lens power

Question 12

Nodal point definition

Answer 12

Point on the axis thru which light PASSES UNDEVIATED

-for an SSRI, the nodal point is the center of curvature

Question 13

Lateral/linear magnification

• definition
• equation

Answer 13

Ratio of image size to object size

m = hi/ho = L/L’ = ℓ’/ℓ
= (height i)/(height o)
= (incoming verg)/(outgoing verg)
= (image dist from lens)/(object dist from lens)

Note: m only = ℓ’/ℓ if the object and image are located in the same index of refraction

Question 14

In the case of a flat surface, ideas from SSRIs lead to an equation for __

Answer 14

Apparent image locations (APPARENT DEPTH)

Question 15

Apparent depth equation

Answer 15

For a flat surf, r = infinity, so F = 0:

(n1/ℓ) = (n2/ℓ’)

*app depth q’s are asking WHERE THE IMAGE IS LOCATED relative to the flat surface (object’s app dist = image location)

Question 16

What Snell’s law describes

Answer 16

Relationship b/w ANGLE OF REFRACTION and ANGLE OF INCIDENCE

Question 17

Snell’s law equation

Answer 17

n1sinφ(i) = n2sinφ(r)

IR1 * sin(angle of incidence) =IR2 * sin(angle of refraction)

Question 18

Describe total internal reflection

Answer 18

For n2 < n1, there exists some angle critical angle (φc) such that light at any angle of incidence φi > φc will be totally internally reflected
-i.e. light incident at an angle greater than critical angle will be reflected internally

Question 19

Total internal reflection stated mathematically

Answer 19

At φi = φc, φr = 90:

Sin(φc) = n2/n1

Note: TIR is ONLY POSSIBLE IF n2 < n1

Question 20

Total internal reflection

-optometry practice

Answer 20

Unaided viewing of anterior chamber angle impossible

TIR is overcome with gonio lenses