Transcript The Vibrating String

The Ray Box: Part Two
Law of Refraction
The law of refraction for light states that a
light ray is bent away from its original direction
when it passes from one medium to another if it
strikes the interface between the two media at
a nonzero angle of incidence.
Normal
Incident Beam
qi
Air
Glass
Refracted Beam
qR
Refraction is the reason why swimming
pools look more shallow than they really
are.
Refraction is the property that explains
the operation of telescopes, binoculars,
eyeglass lenses, projector lenses, etc.
Introduction
In today’s experiment you will continue to
use the properties of reflection and
refraction.
The concepts of color addition and color
subtraction also will be studied.
A short description of light transmission
and reflection with color filters follows.
When light passes from one medium into
another, part of the light is transmitted
into the next medium and part of the light
is reflected back into the first medium.
To show this look at the white light below
that is incident upon a red filter.
There would be multiple reflections
inside the filter, but they would
become weaker with each reflection.
Color Addition
Through color addition you are able to see a wide range of
colors from a color TV or color projector which actually
only emit three different colors.
These colors are red, green, and blue.
They are called the additive primaries.
Your vision system “adds” these together to see a single
color from a single location illuminated by more than one
color.
You can even see colors that don’t appear in the
continuous emission spectrum of the sun.
Red, green, and blue are used as the additive primaries
because this set of three will produce the widest range of
colors that you visually experience.
On the next slide you will see what happens
as you add colors to produce other colors.
Colors in White
White
Red
Green
Blue
You can see that these three add to give white.
Yellow
Note that yellow is the addition of red and green.
Cyan
Magenta
Note that cyan is the addition of green and
blue.
Note that magenta is the addition of red and blue.
To summarize, see color addition circles on next slide.
Color Addition Circles
What you are about to see is what you would get
with three partially overlapping spotlights
reflecting off a white
screen.
Yellow
Red
Green
Cyan
Magenta
Blue
Color Subtraction
Through color subtraction you are able to see a variety of
colors from printings, paintings, etc.
If you have ever bought printer inks, you will notice that
the ones used to provide a variety of colors in printing are
yellow, cyan, and magenta.
They are called the subtractive primaries.
In subtraction colors are eliminated by the absorption of
colors that were in the original illuminating source.
This particular set of three colors, yellow, cyan, and
magenta, will produce the widest range of colors that you
visually experience.
On the next slide you will see what happens
as you remove different colors from white
light.
Colors in White
You get blue.
White
Blue
Yellow
Take away yellow and what is left?
Colors in White
You get red.
White
Red
Cyan
Take away cyan and what is left?
Colors in White
You get green.
White
Green
Magenta
Take away magenta and what is left?
To summarize,
see color
subtraction
circles
on next slide.
Color Subtraction Circles
What you are about to see is what you would get
with three partially overlapping transparencies on
an overhead projector.
Green
Cyan
Yellow
Blue
Red
Magenta
Complementary Colors
Any two colors that add to give white are
said to be complementary colors.
Of the primary colors, both additive and
subtractive, the following pairs are
complementary colors.
Red and Cyan
Green and Magenta
Blue and Yellow
When complementary colors are used in
color subtraction, generally black is
produced.
One exception will show this in the
demonstration that follows.
Your laboratory assistant will now
demonstrate color subtraction using only
complementary colors.
On the next slide you will see what happens
as white light passes through the blue and
yellow filters.
A yellow filter lets this through.
A blue filter lets this through.
It is obvious that green will get
through both filters.
This situation only occurs with this
particular combination of filters.
It is because filters pass a range of colors
and in this case with blue and yellow,
the ranges overlap because blue and yellow
are fairly close to each other in the color
spectrum.