Miscellaneous Flashcards
One meter has the power of how many diopters?
1
Formula to find power of a lens:
F+B=P
(Front of lens + Back of lens = Power of Lens(
1” = _____mm
25.4
Formula to find Focal Length:
F= 1/D
Characteristics of Minus Lenses
- minify image
- thinner middle
- with motion
- are for myopia only
Minus lens shapes
- Bi-concave
- Piano-concave
- Meniscus
Plus Lens Shapes
- Bi-convex
- Plano-convex
- Meniscus
Characteristics of Plus Lenses
- magnifies
- thick center
- against motion
- corrects: hyperopia, presbyopia & aphakia
Light rays become parallel at how many feet?
20 (to infinity unless interrupted)
Three Bands of Ultra Violet Light:
A B C
A & B: use UV protection
C: is absorbed by atmosphere
The separation of Light Rays into Colors is called:
Dispersion
Reverse Slab is made in only:
CR-39 & ST28
It is pre-made on the front of the most plus lens
Purpose of slab off
To balance the prism on bi-focals that have a imbalance due to rx,
Add slab off to grind a new oc on the back of the most minus or least plus lens.
Index of Refraction and ABBÉ value of:
CR-39
1.49
59-60
Index of Refraction and ABBÉ value of:
Crown Glass
1.523
60