Lecture 1 Flashcards
1
Q
Lens ( basic definition)
A
transparent optical medium with two polished surfaces
2
Q
3 general functions of lenses
A
- add vergence to incident light (spectacle lenses)
- protect the eye from mechanical or chemical injury (safety goggles)
- reduces intensity of incident light (sunglasses)
3
Q
3 types of lenses
A
- plano
- convex
- concave
4
Q
Plano lens characteristics
A
- flat surface
- does not change vergence of light
- zero power
- infinitely large radius of curvature
5
Q
Convex lens characteristics
A
- thicker in middle
- surface increases vergence of incident light ie converges light
- plus power
6
Q
Concave lens characteristics
A
- thinner in middle
- surface decreases vergence of incident light ie diverges light
- minus power
7
Q
2 basic lens forms and characteristics
A
- Flat- one plano surface with either convex/concave OR two convex OR two concave
- Meniscus- one convex and one concave surface
8
Q
Curvature (R) formula
A
R= 1/r
R= curvature
r= radius in metres
units of m^-1
9
Q
Optical lens definition
A
An imaginary line that passes through the center of a lens perpendicular to both sides of the lens
10
Q
What is the secondary focal point Fâ ?
A
Point where light rays parallel to optical axis converge or appear to converge after passing through a lens
11
Q
What are the rfractove indices of the following
1. Water
2. Crown glass
3. CR39
4. Poly carbonate
A
- Water-1.33
- Crown glass- 1.523
- CR39 - 1.498
- Poly carbonate- 1.586
