1
Q
Define vergence
A
vergence describes the path of a ray of light
2
Q
what is the sign convention of convergence and divergence and parallel rays
A
convergence = +ve divergence= -ve parallel= zero
3
Q
give two formulas for surface powers?
A
1) F= (n’-n)/r
2) F=L’-L
4
Q
positive lenses are used to correct what?
A
hyperopia and presbyopia
5
Q
negative lenses are used to correct what?
A
myopia
6
Q
what is BVP?
A
the dioptric distance from the back surface of the
lens to the second principle focal point F’.
It represents the power of the lens from the perspective of the person wearing the lens.
7
Q
what is FVP?
A
FVP represents the power of the lens when viewed from the front surface
