Light Theory

Question 1

What is the metric system?

Answer 1

• a standardized system of measurement used globally, based on decimal multiples and prefixes, making it easy to convert between units by simply moving the decimal point
• Also a common unit of measure in optic

Question 2

what is one meter in inches?

Answer 2

39.37 inches

Question 3

What is one centimeter in inches?

Answer 3

0.39 inches

Question 4

What is one inch in centimeters?

Answer 4

2.5 centimeters

Question 5

What does 1 meter equal to decimeters, centimeters, and millimeters?

Answer 5

• 10 decimeters
• 100 centimeters
• 1000 millimeters

Question 6

How many millimeters in 3 meters?

Answer 6

• Convert meters to millimeters: move decimal three places to the right
• 3,000 millimeter

Question 7

What is 8mm converted to meters?

Answer 7

• Convert millimeters to meters: move decimal three places to the left
• 0.008 meters

Question 8

How many millimeters in 3 centimeters?

Answer 8

• Convert millimeters to centimeters: move decimal one place to the right
• 30 millimeters

Question 9

How many centimeters in 6 millimeters?

Answer 9

• Converting centimeters to millimeters: move the decimal one place to the left
• 0.6 centimeter

Question 10

What is visible light?

Answer 10

• Sun and Earth emit electromagnetic energy in varying wavelengths
• Energy radiates in all directions moving in a vibrating wave motion

Question 11

What is wavelength measured in?

Answer 11

nanometers

Question 12

How much can a human eye see wavelengths in nanometers?

Answer 12

Between 308 nm and 750 nm

Question 13

What are the 3 types of ultraviolet light and what are their nanometers?

Answer 13

• UVC : 200 NM TO 290 NM (absorbed by atmosphere)
• UVB: 290 NM TO 315 NM (source of sunburns)
• UVA: 315 NM TO 380 NM (ages skin)

Question 14

Which of the types of ultraviolet light can cause damage to the eye?

Answer 14

UVA and UVB rays

Question 15

What types of objects can cause UV exposure and what are their percentages?

Answer 15

Grass and soul reflect 10%
Sand reflects 15%
Water reflects 25%
Snow reflects 80%

Question 16

What does the color blue in the wavelength do?

Answer 16

• Focus off the retina and contributes to blurry vision
• Shorter higher energy wavelength

Question 17

What is the index of refraction?

Answer 17

Index of refraction= speed of light in air/(divide) speed of light in medium

Question 18

Light will travel in a straight line unless it’s interrupted by an object in its path. What is the angle of incidence?

Answer 18

Is the angel of the incoming ray

Question 19

What is the angel of reflection?

Answer 19

• Is the angle at which the ray leaves the reflecting surface
• The angle of incidence always equals the angle of reflection

Question 20

What happens to the strike of light when hitting a parallel-sided glass block at a perpendicular angle?

Answer 20

Its speed is reduced, but its direction is not changed.

Question 21

What happens when the light strikes a parallel-sided glass block at an angle other than 90 degrees?

Answer 21

The rays will travel slower and will be bent

Question 22

What is the point and flat surface called on a prism?

Answer 22

• Apex is the point
• Base is the flat surface

Question 23

What happens when light passes through a prism?

Answer 23

It redirects the light toward its base

Question 24

What is the formula to measure the power of the prism?

Answer 24

P = C/D
P: prism
C: displacement in cm
D: distance from prism in meters

Question 25

What is the power of a prism that displaces light 1cm at a distance of 0.5 meter?

Answer 25

P= C/D
P= 1cm/0.5m
P= 2.00D

Question 26

What do the plus lenses look like?

Answer 26

It looks like two prism combined base-to-base

Question 27

What do the minus lenses look like?

Answer 27

It looks like two prism combined apex to apex

Question 28

What is the Focal Length formula?

Answer 28

f= 1/F
f: focal length
F: lens power in diopters
D: distance from prism in meters

Question 29

What focal length name does the plus lenses have?

Answer 29

Real

Question 30

What focal length name does the minus lenses have?

Answer 30

Virtual

Question 31

What is the focal length of a +2.00D Lens?

Answer 31

f= 1/F
f= 1/2
f= 0.5m real

Question 32

What is the focal length of a -4.00D lens?

Answer 32

f= 1/F
f=1/4
f=0.25m virtual

Question 33

What is the power of a lens with a virtual 2m focal length?

Answer 33

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

Question 34

What is the optical center?

Answer 34

The single point on the lens through which light may pass without deviated (refracted)

Question 34

What are the plus lens characteristics?

Answer 34

• As the lens moves left the image would move in the opposite direction. (against the motion)
• Plus lenses magnify
• High-plus lenses have a pincushion distortion
• Convex lens

Question 35

What are the minus lens characteristics?

Answer 35

• As the lens moves left the image moves in the same direction. (with the motion)
• Minus lenses minify
• High-minus lenses have barrel distortion
• Concave lenses

Question 36

What happens to the lens power when using a plus lens?

Answer 36

It is when the power of the lenses becomes weaker when they are moved closer to the eye. At the same time, they become stronger when they are pushed further from the eye.

Question 37

What happens to the lens power when using a minus lens?

Answer 37

Minus lens power becomes stronger as lenses are moved closer to the eye. At the same time, they become weaker as lenses are pushed further from the eye.

Question 38

What is the vertex distance formula?

Answer 38

F= Diopters/ (1-dD)
F: effective power
D: True Power
d: distance in meters the lens is moved

Question 39

If a +10.00D lens is moved 5mm further away from the eye, what is its effective power at this new distance?

Answer 39

F= Diopters/(1-dD)
F= 10.00/ (1-0.005x10)
F= 10.52
(mm converts to meters for d)