Unit 1: Review Of Optics

Question 1

What reference points can we use to measure the PD if we don’t have a penlight?

Answer 1

Inner limbus to outer limbus

Question 2

Formula for compensating for a different index from your lens clock

Answer 2

Dt=R[(n-1)/(n2-1)

Where Dt is the true power
R=reading on the lens clock
n=index of the material
n2=index of the lens clock

Question 3

Materials with centre thicknesses of 2 mm

Answer 3

-CR-39
-Crown glass
-1.74 index glass

Question 4

Materials with centre thicknesses of 1 mm

Answer 4

-Trivex
-Polycarbonate
-1.74 plastic
-Other high index plastic

Question 5

Materials with centre thicknesses of 1.5 mm

Answer 5

-Spectralite
-Polyurethane
-1.6 index glass

Question 6

What is the approximate formula?

Answer 6

F(theta)= cyl(sin(theta))squared + sph

Question 7

When would you use the approximate formula?

Answer 7

To find the power in oblique meridians

Question 8

What is the equation of finding the dioptric power from a focal length?

Answer 8

D=1/f

D=dioptric power
f= focal length IN METERS

Question 9

How to use the focal length equation with inches

Answer 9

D=39.37/f

OR Multiply inches by 0.0254 and put result into regular focal length equation.

Question 10

What’s the focal length equation when not in air?

Answer 10

D=n/f

D=diopters
n= index of material
f= focal length

Question 11

How to find the index of refraction

Answer 11

n=(speed of light in air)/(speed of light in substance)

Question 12

What is Snells law?

Answer 12

n1(sintheta1)=n2(sintheta2)