metric conversion

1 meter =39.37inches

1DM= 1/10 of a meter

1cm=1/100th of a meter

1mm= 1/1000th of a meter

1 nm(nanometer) 1 billionth of a meter

1DM= 1/10 of a meter

1cm=1/100th of a meter

1mm= 1/1000th of a meter

1 nm(nanometer) 1 billionth of a meter

visible light spectrum or “white light”

between 380nm and 750nm

ROY G BIV

colors of the visible light spectrum

red, orange, yellow, blue, green, indigo, violet

red, orange, yellow, blue, green, indigo, violet

Red

650 to 750nm

Orange

590 to 650 nm

yellow

560 to 590 nm

blue

500 to 560 nm

green

470 to 500nm

violet

380 470nm

dispersion

The term that refers to the breaking up of light into its component colors

chromatic abberation

dispersion is a characteristic of this common lens aberration

invisible light spectrum

ultraviolet light below 380nm (harmful)

infra red light above 750nm (not harmful)

infra red light above 750nm (not harmful)

UVA

330 to 380nm harmful to they eye

UVB

275 to 330nm sunburn

UVC

200 to 275nm very dangerous

Infrared

Infrared is experienced by the wearer as heat energy. While no specific harmful effect has been proven, unprotected eyes in the bright sunlight can be fatigued easily. Above 750nm, long waves/low energy/ not harmful

light ray

unless interrupted it will travel in a straight line

angle of incedence

angle at which an incoming light ray strikes a surface

normal

an imaginary line that is perpendicular to the reflecting surface

angle of reflection

the angle a which a light ray leaves the reflecting surface

in-phase

When two waves are vibrating in a parallel peak-peak / trough-trough pattern. When two waves are in-phase, constructive interference takes place. Like 1 + 1 = 2, the two smaller waves combine to form one larger one that is equal to the sum of the two.

out-of-phase

When waves are vibrating in a parallel peak-trough pattern,The waves are equal, but opposite, so they cancel one another out.

out-of-phase A/R

An AR coating is formulated to create an out of phase alignment between the 4% front reflection loss and the 4% back reflection loss. The result is 99.5% transmission, virtually no reflection, thus an invisible lens.

Light/ refraction A.

the particulars of refraction are explained by Snell’s Law. 1. When light strikes a clear medium around 8% is reflected 2. Less than 1% is absorbed 3. approx 92% of light passes through. the path a ray of light will take trough a medium depends on the angle of incidence and the index of refraction of the medium.

Light/ refraction B.

From a less dense medium to a more dense medium the speed of light will be slowed. The path of the light will bend towards the normal. From a more dense medium to a less dense medium the speed of light will increase and return to 186,000 miles per sec. the path will move away from the normal. The incidence path and the exiting path will be parallel

Light/ refraction C.

when light strikes a transparent medium in a perpendicular manner no bending or refraction takes place. Angle of refraction: exists between normal and the ray path inside the medium.

Angle of deviation: exists between the ray path and the imaginary extension of the undeviated ray.

Angle of deviation: exists between the ray path and the imaginary extension of the undeviated ray.

Factors that affect the amount of refraction

1. as angle of incidence gets greater the refraction that will take place gets greater. 2. great the index of refraction of the medium the greater the refraction of light 3. rays that strike the medium on a perpendicular path will not be refracted

Light schematic

A light ray enters a denser medium and it bends down towards the normal. The angle between the incoming ray and the normal is the angle of incidence. The angle between the imaginary path that the ray would have taken had it been un-deviated and where it actually ends up is the angle of deviation. The angle between the actual refracted ray and the normal is the angle of refraction

index of refraction

speed of light in air divided by the speed of light in the medium. Ex:186,000/124,832=1.49(CR-39)

diamond

2.41

thindex glass

1.80

Hi-lite glass

1.74

flint glass

1.69

polyurethane plastic

1.60

polycarbonate

1.59

crown glass

1.53

cr-39

1.49

water

1.33

surface lab standard

1.53

Characteristics of a plus lens

1. convergeses

2. “real focal point”

3. magnifies

4. against motion

5 Center thicker than the edge

6. Weakens as vertex shortens

2. “real focal point”

3. magnifies

4. against motion

5 Center thicker than the edge

6. Weakens as vertex shortens

Characteristics of a minus lens

1. Diverges

2. “virtual image”

3 minifies

4 with motion

5 center thinner than edge

6 strengthens as vertex shortens

2. “virtual image”

3 minifies

4 with motion

5 center thinner than edge

6 strengthens as vertex shortens

Focal length

can be defined as the distance a lens takes to focus parallel beams of light. Stronger lenses have shorter focal lengths and weaker lenses have longer focal lengths

focal length pt. 2

. Remember that if a one-diopter lens focuses at a distance of one meter, a two-diopter lens (since it is twice as strong) will focus in half that distance, or one-half of a meter. A .50-diopter lens (since it is half as strong ) will focus at twice the distance, or two meters.

formula: focal length in meters

1 divided by dioptric power

Ex: 1/10= 1/10 of a meter or 10cm or 100mm

Ex: 1/10= 1/10 of a meter or 10cm or 100mm

formula: dioptric power

1 divided by focal length in meters

Ex: what is the dioptric power of a lens whose focal length is 2 meters? 1/2 or .50 diopter

Ex: what is the dioptric power of a lens whose focal length is 2 meters? 1/2 or .50 diopter

abbe Value of Crown glass

60

abbe value of Cr-39

57

abbe value of polyurethane plastic

37

abbe value of flint glass

36

abbe value of polycarbonate

30