FORMULAS Flashcards
1
Q
Prentices formula
A
P=C(D)
2
Q
Approximate formula
A
FT= FC(sin0)^2 + FS
3
Q
Lens thickness / Sag depth
A
Sag = r square root r2 - (d/2) ^2
4
Q
Approx thickness / Sag
A
Sag = (d/2)^2 D / 2000 (n-1)
5
Q
Index of refraction
A
n= c/v
6
Q
Nominal power
A
FT = F1 + F2
7
Q
Focal Length
A
P= 1/f
8
Q
Lens compensation
A
DT = R (n-1) / (n-2)
9
Q
Snells law
A
ni (sin01) = nr (Sin0r)
10
Q
Verticle Decentration
A
OC - B/2
11
Q
Horizontal Decentration
A
A + DBL / 2 - MONO PD
12
Q
Minimum blank size
A
ED + 2 (decentration) + 2
13
Q
Binocular decentration
A
frame PD - Px PD / 2
14
Q
Effectivr power
A
De = DI / 1 + d (DI)
15
Q
Compensated power
A
Dc = DI / 1 - d (DI)
16
Q
mm to m
A
divide by 1000
17
Q
mm to cm
A
divide by 10
18
Q
TOTAL INSET
A
Frame PD - mono PD x 2
19
Q
SEGMENT INSET
A
1/2 (PD DISTANCE - PD NEAR)
20
Q
Seg drop
A
B / 2 - seg h
