Handout 4

Question 1

the normal, imaginary line connecting the centers of curvature of the two surfaces of the lens

Answer 1

optic axis

Question 2

the point on the optic axis intersected by the path of a ray of light between the 2 surfaces that, after refraction by the second surface, is parallel to its path before the incidence at the first surface (no prismatic effect)

Answer 2

optic center

Question 3

spherical, homocentric, sitgmatic lenses refract light how?

Answer 3

light rays meet at one common point, convex and concave

Question 4

cylindrical, astigatism kens refract light how?

Answer 4

light rays to focal LINE

Question 5

toric, spherocyl, astig., nonhomocentric refract light how?

Answer 5

light rays to form two line images perpendicular from each other

Question 6

the change in vergence that occurs when light passes through a lens

Answer 6

refractive power

Question 7

approximate power aka is measure with

Answer 7

nominal power,lens clock

Question 8

lens power specified in terms of front and back surface powers with out regards to thickness

Answer 8

approximate power,nominal power

Question 9

series of lenses separated by air, having different index of refractions are called

Answer 9

equivalent systems /equivalent power

Question 10

both are specified in terms of refracting power for emergent rays of light at the back or front surface of the system

Answer 10

front vertex power and back vertex power

Question 11

front vertex power aka

Answer 11

neutralizing

Question 12

typically measure using hand neutralization, and using a focimeter by placing front surface of lens

Answer 12

front vertex/neutralizing power

Question 13

the ability of the lens to focus parallel rays of light at a given plane

Answer 13

effective power

Question 14

the greter the effect on vergence

Answer 14

the more effective the lens is

Question 15

the lens power needed to correct a pts ametropia is dependent on

Answer 15

the distance from wearers eyes

Question 16

effective power aka

Answer 16

back vertex power

Question 17

is used to indicate the change in lens power required if a lens is moved from one position to another

Answer 17

effective power

Question 18

Feff : as lenses are moved further from the eye

Answer 18

plus power increases

Question 19

Feff: as lenes are moved closer to the eye

Answer 19

minus power increases

Question 20

> -4.00 D will require contact lens

Answer 20

lesser power

Question 21

> +4.00 D will require contacts

Answer 21

higher power

Question 22

if a presbyope is oving their glasses low they may need

Answer 22

a more effective plus lens

Question 23

lens clock measures

Answer 23

powers of front and back surface power according to sag

Question 24

the focimeter measures

Answer 24

vertex power of a lens

Question 25

focusing system of the focimeter includes

Answer 25

light source + movable target + standard lems + lens stop

Question 26

observation system

Answer 26

low powered keplerian telescope w/ an objective lens a secondary focal plae of the obj lens and an adjustable eyepiece