Optics

Question 1

Transverse Mag=?

Answer 1

MAG=I/O=V/U

Image/Object=Mag

Question 2

What is the equation for focal length?

Answer 2

f= 1/D

Question 3

What is the equation for spherical equivalent?

Answer 3

Spherical equivalent= (sphere) +(1/2)(cylinder)

Question 4

What is the equation for axial magnification?

Answer 4

MAGaxial= (MAGtransverse)^2

Question 5

What is the equation for a simple magnifier?

Answer 5

Mag= Diopter/4

Question 6

What is the equation for telescope magnification?

Answer 6

Mag= Deyepiece/Dobjective

Question 7

What is the relationship of mag to spectacle power?

Answer 7

Mag= 2% per diopter of power

Question 8

What is the equation of the basic lens formula?

Answer 8

U+D=V

U=vergence of light entering lens
D=power of lens
V=vergence of light leaving the lens

Question 9

What is the refracting power of a spherical surface?

Answer 9

Ds = (n’-n)/r

n'-n = difference in refractive index
r= radius of curvature of surface(meters)

Wether D power is + or - is determined by drawing a rectangle around the interface and shading the side with the higher index.

Question 10

What is the equation for a lens immersed in fluid?

Answer 10

D air/D fluid= (n lens - n air)/(n lens - n fluid)

Question 11

What is the equation to determine retinal image height in a schematic eye?

Answer 11

(Object height)/(retinal image height) = (distance from nodal point)/17mm

All in mm

Question 12

Where is the focal point in hyperopia and myopia?

Answer 12

Hyperopia= focal point is behind the retina

Myopia= focal point is in front of the retina

Question 13

What does moving a lens do to its refractive power?

Answer 13

Moving a lens forward increases its effective plus power(decreases effective minus)

Moving a lens backward(toward patient) decreases its effective plus power(increases effective minus)

Question 14

What is the SRK formula?

Answer 14

P = A - (2.5 L) - (0.9 K)

A = given constant (fudge factor)
L =  axial length in mm
K = average corneal curvature(in D)

Question 15

What is prentice’s rule?

Answer 15

Prism diopter = h(in cm) D

h = height in cm from optical center
D = diopter of lens

( minus act like base up above and base down below)

( plus act like base down above and base up below)