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Dispensing Optician > Formulas and Optical Theory > Flashcards

Formulas and Optical Theory Flashcards

1
Q

TP = sphere power + cylinder power x sin 2 (0)

A

Power in Oblique meridians

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2
Q

N1 sin i = N2 sin r

A

Snells’ Law

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3
Q

angle I =angle r

A

Law of reflection

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4
Q

Prism (^)=(hxD) / 10

A

Prentice Rule

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5
Q

D = 1/f

A

Focal length - Dioptic power

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6
Q

De = D1 +D2

A

Nominal Power

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7
Q

FPD = A +DBL

A

Frame PD

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8
Q

Dec = (FPD - PPD) / 2

A

Binocular decentration

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9
Q

Speed of light in air/ speed of light in medium.

A

Index of refraction

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10
Q

MBS = ED + (2 X Dec)

A

Minimum blank size

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11
Q

I need a lens with power +3.50D. If I use a lens blank with a front surface power of +8.00D, what back surface do I need?

A

De = D1 + D2 +3.50 = +8.00 + D2 D2 = -4.50

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12
Q

I have a lens with a front surface of +9.25D and a back surface of -2.25D. What is the power of the lens?

A

De = D1 +D2 De = +9.25 + -2.25 De = +7.00

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13
Q

I want my lens to have a power of -3.00D. What back surface do I need if the front surface is +8.00D?

A

De = D1 +D2 -3.00 = +8.00 +D2 D2= -11.00

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14
Q

What is the difference between a high index lens and a aspheric lens?

A

High index refers to the material of the lens; Aspheric refers to the surface design of the lens

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15
Q

What are the three things that can happen to a ray of light when it passes through a lens?

A

Absorbed, reflected, refracted

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16
Q

What is the difference between a monocular distance PD and a binocular distance PD?

A

Monocular PD: each eye is measured separately from the center line of the face
Binocular PD: the measurement is taken from the center pupil to center pupil

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17
Q

What role does the Food and Drug Administration play in the ophthalmic industry?

A

They are responsible for the lens safety aspect of the industry. Impact resistance is their main focus.

18
Q

According to the Systems text, eyewear can be divided in to what three categories?

A

Dress eye wear - Designed for everyday use.

Safety eyewear - Designed to meet higher standards of impact resistance since it will be worn in situations that could be potentially hazardous to the eyes.

Sports eyewear - Designed to protect the eyes or enhance the vision in specific sports situations. What is appropriate will vary dramatically depending upon the sport.

19
Q

What are the Rx’s in a plus cylinder form of the following optical crosses?

  • 1.00 @095 -3.00 @ 175
    - 2.00 @005 +1.50 @ 085
A

-2.00 + 1.00 x 005 -3.00 + 4.50 x 175

20
Q

What is transposition?

A

Transposition is the changing of a prescription from a plus cylinder to a minus cylinder or the other way around. It does not affect the powers of the prescription.

21
Q

What is the dioptric power a lens with a focal length of _____?

  1. ) 40 mm
  2. ) -33 mm
A
  1. ) D = 1/f D = 1 / .04 D = +2.50

2. ) D= 1/f D = 1 / .33 D = -3.00

22
Q

What is the focal length of a -2.00 D lens in meters?

A

F = 1D F = 1/-2 F = -0.50 meters

23
Q

What type of image is formed by a minus lens?

A

Virtual

24
Q

A plus lens does what to light rays that pass through it?

A

Makes them converge

25
Q

What does the term critical angle of a material mean?

A

The ray of light is striking the surface at an angle so that the ray is refracted along the surface of the lens.

26
Q

What is the lens power in the 90th meridian for this lens prescription: +3.00 +1.00 x 180

a. +1.00
b. +2.00
c. +3.00
d. +4.00

A

+4.00

27
Q

A minus lens with the optical center moved up created _____.

a. base up prism
b. base in prism
c. base out prism
d. base down prism

A

base down prism

28
Q

A base-up prism _____.

a. bends light towards the base
b. bends light rays away from the apex
c. projects an image of the object downwards
d. all of the above

A

all of the above

29
Q

The wavelengths of visible light range approximately from _____.

a. 200 - 400 nanometers
b. 300 - 600 nanometers
c. 400 - 720 nanometers
d. 500 - 800 nanometers

A

400 - 720 nanometers

30
Q

The wavelengths of light that are the most pleasing to the eye are _____.

a. ultra-violet
b. infra-red
c. blue-green
d. orange

A

blue-green

31
Q

The breakdown of light into its component colors is called _____.

a. dispersion
b. refraction
c. reflection
d. aberration

A

refraction

32
Q

The point on a lens which a ray of light will pass through without being deviated is called _____.

a. apex
b. base
c. optical zone
d. optical center

A

optical center

33
Q

The lower the abbe number, the _____.

a. less the chromatic aberration
b. more the chromatic aberration
c. thicker the lens
d. thinner the lens

A

more the chromatic aberration

34
Q

If a lens deviates a ray of light 4 cm at a distance of 2 meters, the lens is said to have power of _____ diopters?

a. .25
b. .50
c. 1.00
d. 2.00

A

2.00

35
Q

The transposed Rx of +3.00 - 1.00 x 30 is _____.

a. +3.00 +1.00 x120
b. +2.00 -1.00 x 30
c. +2.00 +1.00 x120
d. +2.00 -1.00 x 30

A

+2.00 +1.00 x 120

36
Q

Which lens has the characteristic of magnification?

a. Minus spherical
b. Plus spherical

A

Plus spherical

37
Q

Which lens has the characteristic of thin center/thick edge?

a. Minus spherical
b. Plus spherical

A

Minus spherical

38
Q

Which lens has the characteristic of diverging light rays?

a. Minus spherical
b. Plus spherical

A

Minus spherical

39
Q

Which lens has the characteristic of with motion?

a. Minus spherical
b. Plus spherical

A

Minus spherical

40
Q

The lens design in which the front base curve gradually flattens is called _____.

a. aspherical
b. spherical
c. corrected curve
d. meniscus

A

aspherical

41
Q

Plus lenses _____.

a. are diverging lenses
b. are thicker at the center than the edge
c. minify image size
d. show with motion

A

are thicker at the center then the edge

Dispensing Optician (18 decks)

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