Light Theory Flashcards
1 m=___inches
39.37 inches
1 cm=___inches
0.39 inches
1 in=___centimeters
2.5 cm.
1 m=___decimeters
10 decimeters
1 m=___centimeters
100 cm
1 m=___millimeters
1000 mm
Frame parts and lenses are usually measured in what?
millimeters.
What is the electromagnetic wave theory?
Explains how light works. The sun and earth emit electromagnetic energy in varying wavelengths.
Where does electromagnetic energy come from?
The Sun and Earth .
Where does the energy radiate? In what motion?
The energy radiates in ALL directions and moves in a vibrating wave motion.
What is a wavelength?
A wavelength is the distance between pulsations and is measured in nanometers.
What are the two sections of the electromagnetic spectrum according to the wavelengths?
At one end is the shortest and the MOST energetic waves called gamma rays.
At the other end is the longest such as radio waves.
What is a shorter wavelength next to visible light?
UV rays.
What is a longer wavelength next to the visible light?
Infrared Rays.
What range of wavelengths that the human eye can see?
Approx. 380nm-750nm
What are the 3 types of UV light?
UVA, UVB,UVC.
How long is the wavelength of UVC?
200-290nm
What does UVC do?
It is absorbed by the atmosphere.
How long is the wavelength of UVB?
290-315nm
What does UVB do?
It is the source of sunburns.
How long is the wavelength of UVA?
315-380nm
What does UVA do?
Ages skin.
What types of UVs damages the eye?
UVA and UVB
Where can UV exposures increase?
reflections off of surfaces.
How much UV exposure does the grass and soil reflect?
10%
How much UV exposure does the sand reflect?
15%
How much UV exposure does the water reflect?
25%
How much UV exposure does the snow reflect?
80%
What is visible light?
A combination of all colors of the spectrum
What happens when light enters the prism?
Each specific wavelength is slowed and bent to a different degree.
What is the result of when light enters the prism?
This electromagnetic phenomenon is a rainbow that has been split into separate parts.
How is the cooler blue defined in the spectrum?
shorter, higher energy wavelengths.
Blue rays have the tendency to focus off the retina and because of that it may cause blurry vision.
Where are the green waves located?
Central portion of the spectrum.
What do green waves convey?
conveys the clearest vision.
What is the term of index of refraction refer to?
the relationship between the speed of light in air and the speed of light in any given medium.
How fast is the speed of light in air?
186,000 miles per second.
What happens as the density of a material increases?
that material has the ability to bend light.
How is the example of the 1.49 index of refraction for a CR-39 plastic lens calculated?
Simply divide the speed light in CR-39 into the speed of light in air to arrive at the index of refraction of 1.49.
What’s the formula of finding the index of refraction?
speed of light in air
___________________
speed of light in medium
What does the index of refraction help determine?
The lens thickness.
An index refraction as HIGH as 1.8 are noticeably…?
thinner, it is rarely used because glass lenses are heavy and break more easily.
What is the index refraction for a surfacing lab standard?
trivex 1.53
Describe how a ray of light would travel.
in a straight in a line unless interrupted by an object in its path.
What is the term of an incoming ray strikes the surface ?
Angle of incidence.
What is the term of a ray leaving a surface?
Angle of reflection
When light strikes a parallel sided glass block at a perpendicular angle, its speed is …?
reduced but the direction is not changed. So light rays that strike a refracting surface in a perpendicular path will not be refracted.
When light strikes a parallel sided glass at an angle other than 90 degree, the light rays will travel ….?
slower and will be bent. The amount of displacement depends on the thickness of the slab.
What does the angle of incidence always equal?
angle of reflection.
When can the angle of refraction can be calculated?
If the refractive indices of both mediums the light is traveling through are known.
What formula is used to calculate the angle of refraction?
The Snell’s law.
