Resultant Prism= - correct answer. The square root of (Vertical prism^2) + (Horizontal
prism^2)
tan a=V/H
Shape Factor= - correct answer. 1/1-(T/NxF)
T=center thickness in m
N= index of refraction of lens material
F= front base curve
Power Factor= - correct answer. 1/1-(HxD)
H= vertex distance plus 3 mm in m
D= Dioptric power
Spectacle Magnification= - correct answer. shape factor x power factor
1/ 1-(T/NxF) x 1/1-(HxD)
Power in Oblique Meridians= - correct answer. Total power = sphere power + cyl
power x sin^2 (O)
Snell's Law= - correct answer. N1 sin i = N2 sin r
N1= index of refraction of incident medium
i= angle of incidence
N2= index of refraction of refracting medium
r= angle of refraction
Angle of reflection= - correct answer. angle I= angle r
I= angle of incidence
, r= angle of reflection
Angle of incidence= - correct answer. I=r+d
I= angle of incidence
r= angle of refraction
d= deviation
Index of refraction= - correct answer. Speed of light in a vacuum/Speed of light in the
medium
Prentice Rule= - correct answer. Prism= (hxd)/10
h=distance moved in mm
D= total dioptric power for the meridian
Thick Lens Back Vertex Power= - correct answer. De= D1+D2+ (t/n x D1^2)
De= effective, vertex or lensometer power
D1= true power of the front curve
D2= ture power of the back curve
t= lens thickness in meters
n= index of refraction
Focal length - correct answer. D=1/f
D= dioptric power
f= focal length in meters
Dioptric formula - correct answer. f=1/D
D= dioptric power
f= focal length in meters
Vertex power compensation (if the wearing vertex is less than the refractive vertex)= -
correct answer. Fb= (Fa)/ 1-(dFa)
Fa= primary focal length of the refractive vertex
Fb= Compensated power
d= distance in meters that the lens is moved from the refractive vertex to the wearing
vertex
Vertex power compensation (if the wearing vertex is more than the refractive vertex)= -
correct answer. Fb= (Fa)/ 1+(dFa)
Fa= primary focal length of the refractive vertex
Fb= Compensated power
d= distance in meters that the lens is moved from the refractive vertex to the wearing
vertex
What is the vertex power compensation for a low powered lens? - correct answer. Per
mm= (D^2)/1000
D= dioptric power
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