section A: ol

Question 1

How to find power

Answer 1

n/f

Question 2

different n available

Answer 2

1 =m
100=cm
1000=m

Question 3

how to find combination

Answer 3

turn all f into F
add up F’s ( because focus lengths are not additive)
100/F = Total f cm

Question 4

finding power with radius

Answer 4

F1 = (n-1) / r1
F2 =(1-n) / r2
n is is either front of back depending where the surface is

Question 5

finding radius

Answer 5

R1 = (n-1) / F1
R2 = (1-n) / F2

Question 6

Definition of lenses

Answer 6

lens is aways transparent optical media bounded by two polished surfaces, at least one must be curved
used to cut out radiation

Question 7

Optical media are:

Answer 7

natural occurring material, glass and plastic

Question 8

Dioptre

Answer 8

unit for a focal power is Dioptre

Question 9

finding power with focal

Answer 9

F = 1/focal length = Fm

Question 10

how to find total lens power

Answer 10

F = F1 + F2

Question 11

what are quarter steps

Answer 11

-1.00 . -0.75 . -0.50 . -0.25

Question 12

What are 0.12 steps

Answer 12

0.12 . 0.24 . 0.37

Question 13

what is a flat form/plano confex/ Plano concave

Answer 13

Plano concave =
 F1 = infinity
f2 = +....
Plano Convex
F1 - infinity
F2 = -...

Question 14

Bi convex lens?

Answer 14

F1 = +…
F2 =+…
both plus
bi concave is opposite

Question 15

Meniscus lens?

Answer 15

F1 = +...
F2 = -...

Question 16

how to work out sign for a radius

Answer 16

From front surface to centre = positive

from back surface to centre = negative

Question 17

How to transpose from cross cyl to sphere cyl

Answer 17

Choose a cyl to make phere
use the axis where cyl was not chosen
how much is takes to get to the other cyl not chose =cyl

+3.00 x 180 / +2.00 x 90
= +3.00/ -1.00 x 90
or
= +2.00/ +1.00 x 180

Question 18

how to relate a rx combination

Answer 18

Transpose so at least 2 matching section of axis
then add each section together
then the remaining together = replacement rx

Question 19

what is minimum plate thickness

Answer 19

the thickness of a flat pale of glass from which the lens can be made