Blue Eyes Technology Ppt by ngs16982

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									Christine Schnittka

                          The Science and Technology of Color

Activity Overview
In this activity, students investigate some physical properties of color. Color, as it is
perceived by the human eye, is actually an electromagnetic wave of visible light. The eye
can detect over 10 million colors, through the use of receptors on the retina called rods
and cones. Students will be using a digital camera attached to the computer to photograph
a spectrum of color, and then they will analyze these colors in terms of the frequency,
wavelength, Red/Green/Blue values, and Cyan/Magenta/Yellow values. They will
investigate how colored lights are combined to produce specific colors, and how colored
inks are used on paper as well. They will also learn how to create a simple webpage
which displays the colors in the spectra they photographed.

Advantages of Technology
Through the use of computer technology and peripherals, students can capture colors,
analyze them, and reproduce them in light and ink. Learning becomes a creative activity
in this lesson, and the information that will be gathered and examined cannot be obtained
through print media alone.

Educational Standards
Virginia Standards of Learning addressed in this activity include:
PS.9 The student will investigate and understand the nature and technological
applications of light.
Key concepts include
a) the wave behavior of light (reflection, refraction, diffraction, and interference);
b) images formed by lenses and mirrors; and
c) the electromagnetic spectrum.

   Computer with Internet access and Java virtual engine installed (
   Digital camera attached to computer
   Camerascope software, free to download from
   Color printer
   Paint program (provided by Microsoft operating systems)
   Notepad program (provided by Microsoft operating systems)
   Spectra program, free to download from
   PowerPoint program, to show the slideshow, Color Images, which includes
      student directions, and the images contained in this lesson.

Christine Schnittka

Procedure 1: Additive Colors of Light
Light may appear colorless, but it is actually composed of a spectrum of many colors, all
the colors of the rainbow. We see these colors because our eyes have color receptors
called cone cells, located on our retinas. Yet, oddly enough, our eyes can only detect
three colors, which we call the three primary colors of light. How is it that our brain sees
so many millions of colors with eyes that only have the ability to see three? Use the
following applet to investigate this question.

                               Additive Colors applet screenshot

Assessment: Ask your class the following questions:
How does the eye see white if the cone cells only see color?
How does the eye see yellow?
The primary colors of light are red, green, and blue. The secondary colors are yellow,
cyan (light blue) and magenta (hot pink). Devise a code for creating these secondary
colors. Example: R+B=Y

Most children are taught that the primary colors are red, blue and yellow, so this activity
may surprise your students. The secondary colors of light are created when two primary
colors are added, or when a primary color is taken away from white light. Cyan is
actually white light without red. Yellow is actually white light without blue. Show your
students the following equations and see if they can relate them to what the applet shows:

Since W=(R+B+G),
Then (W-R) = (B+G).
Therefore, W-R = Cyan because B+G = Cyan.

Christine Schnittka

Procedure 2: Subtractive Colors of Light
What would happen to white light if all the primary colors are subtracted, not just one? If
all three primary colors are taken away, no light is left. The color is black. Ask your
students if they could make black light? The first thing they may think of is a “black
light” used in haunted houses and such. Inform you students that black lights put off
white light that has been filtered, but light is still coming out of the bulb. Use the
following applet to investigate the question of how to make” black light”.

                             Subtractive Colors applet screenshot

Note that this applet shows what happens when a primary color is subtracted from white
light. When blue is subtracted from white light, you have yellow. Cyan and magenta are
also formed by subtracting one primary color of light from white light. When al three
primary colors are subtracted, we have the absence of light which we call black. When
cyan, magenta, and yellow are added, all three primary colors of light are essentially
subtracted, and no light is left.

Assessment: Ask your students the following questions:
How does your eye perceive black if the cone cells only see color?
Devise a code for creating black. If W=R+B+G, then what is black?

Christine Schnittka

Procedure 3: Television and Computer Displays
Your computer display creates black much the same way that your eye does, because the
display is composed of tiny dots of red, green and blue light. Each dot of light is called a
Pixel, which means “picture element”. When none of these lights are turned on in a pixel,
the screen is black. Show your students the following close-up images of a television
screen. On the right, in the magnified view, you can see the individual pixels.

Procedure 4: Colored Paints and Inks
Much like a computer screen, a color printer can create a multitude of hues with only
three ink colors, but a printer uses the secondary colors for its ink. That way, it can make
black without even using black ink at all. Recall that combining all three secondary
colors of light is like subtracting all the primary colors of light. Ask your students if they
have ever replaced the ink cartridges on a color printer, and what colors the inks were?
Show your students the following close-up image of a pictures created with a color

Christine Schnittka

Procedure 5: The Electromagnetic Spectrum of Visible Light
Visible light consists of electromagnetic waves within a range of frequencies and
wavelengths. Visible light can be detected by the human eye if it is between wavelengths
of 400 – 700 nanometers. Each wavelength has a characteristic color. A prism can be
used to separate white light into this spectrum of colors, much like a rainbow does.
Astronomers can also use a diffraction grating, a film covered with microscopic grooves,
to separate the light coming from stars into spectra. The spectrum from a distant star can
be analyzed and compared to the spectrum from our own sun. Prisms and diffraction
gratings work because each different wavelength of light bends at a different angle when
it passes through.

Assessment: Ask your students the following questions:
Have you ever used a prism or diffraction grating?
How do you think they work?
Look around you and see if there’s anything in this room that could be used to separate
light into its different wavelengths like a prism or a diffraction grating does?

Then show your students the following images of spectra:

Christine Schnittka

Procedure 6: Spectra
Download the following free program: Spectra
Install the software, and have students explore its uses. In the Visible Light section, move
your cursor back and forth along the spectrum, observing the wavelength and frequency
displayed near the Color Box. The unit symbol, “nm” represents nanometer, 10 9 meter,
or one billionth of a meter. The unit symbol, “THz” represents terahertz, 1012 Hertz, or
one trillion cycles per second.

                                     Spectra screenshot

Light from other hot or burning objects may not contain all of these colors. By looking at
the spectra from different light sources, we can understand what elements are creating
that light. This was discovered in 1814 by Joseph Fraunhofer,
with further discoveries made in 1859 by Gustav Kirchhoff
and Robert Bunsen.

Assessment: Ask your students the following questions:
What color seems to dominate the spectrum of visible light?
Why might this be?
What other observations can you make about the spectrum?
What do you think R G and B stand for under the Color Box?

Christine Schnittka

Procedure 7: Photographing a Spectrum
When you asked your students to look around the room and find an object that would
separate light into its colors, did they mention a compact disk (a CD-ROM or CD-R)?
The back side of a CD behaves like a particular type of diffraction grating called a
reflection grating. The spiraling rows and rows of little pits on the surface of the CD
don’t transmit light like a diffraction grating would; they bend and reflect the light. Each
wavelength of light is bent a different amount, which separates the light into colors. The
pits are so tiny and so close together, only 1.6 micrometers apart, that they cannot be seen
with an ordinary microscope. When light reflects out of these pits, red light from the
spectrum is bent the most, approximately 24°. Purple light is bent the least, 14.5°. This
separation of light is called dispersion.

Download the free software, CameraScope, from
and use this software, along with a web camera, to photograph a spectrum on a CD. Hold
the CD so that light from a window or a lamp bounces off its back side. If the light in the
room is strong enough, you may be able to photograph the reflected spectrum as it falls
on a wall or piece of white paper.

                                  CameraScope screenshot

If you do not have access to a web camera, you can use other digital cameras too, or you
can use some of these images for your students to observe and analyze.

Christine Schnittka

   Christine Schnittka

   Procedure 8: Analyzing the Spectrum
   Use the Windows program, Paint, to examine the photographed spectrum.

Dropper Tool

                                        Paint Screenshot

   To analyze the colors of the spectrum, select the dropper tool and click on a color.
   Click Colors, Edit Colors, Define Custom Colors, and take a look at the Red Green Blue
   section. These values are used in computer technology to describe a color in terms of the
   amount of primary light colors, from a range of 0 – 255. Have your students do this for
   several colors on the spectrum while they record their findings on the Student Worksheet.

   See if your students can compare their spectrum with the Spectra image. Can they
   estimate the frequency and wavelength of each color in their spectra? Sliding the cursor
   over the Spectra image displays these values in the lower right-hand corner of the display.
   Have them record these estimates in the Student Worksheet.

   Assessment: Ask your students the following questions:
   Does your photo resemble the spectrum shown in the program, Spectra?
   Why might it be different?
   Can you see a pattern in the RGB values of each color of light?
   Use the following formula to calculate the speed of light:
   speed of light “c” = frequency (f) x wavelength (λ)

Christine Schnittka

Procedure 9: Light to Ink
In the computer industry, RGB values range from 0-255. RGB values can be converted to
CMY values used by printers to specify the amount of cyan, magenta, and yellow inks to
be used. CMY values are given in a decimal range from 0-1, or a percent range from 0% -
100%. Can your students use their equations for cyan, magenta, and yellow to determine
the CMY values for the colors in their spectrum? In case this proves too difficult, here are
the equations:
C=1-(R/255) x100%
M=1-(G/255) x100%
Y=1-(B/255) x100%
Have your students do these conversions, recording their results on the Student

Procedure 10: HEX Codes for Web Pages
While RGB values are coded in the standard base-10 way, webpage developers have
special codes called HEX codes for the multitude of colors they can use for their designs.
The Base-10 method uses ten digits to represent a value: 0,1,2,3,4,5,6,7,8,and 9. HEX is a
Base-16 method, using combinations of sixteen digits to represent a value:
0,1,2,3,4,5,6,7,8,9,A,B,C,D,E, and F. Converting RGB values into HEX codes is fun, but
it is time consuming. If you want to learn how to do this yourself and teach your students,
see the document, Converting RGB to HEX. Otherwise, access the following website,
hex converter.htm for a simple calculator that converts RGB values into HEX codes.
Have your student use this calculator and record their results on the Student Worksheet. .
After doing this conversion, your students can very easily create a simple webpage using
these HEX codes for their spectrum colors.

                                  RGB to HEX Calculator

Christine Schnittka

Procedure 11: Making a Spectrum Webpage
Open the webpage template, specweb template.txt with the Windows program, Notepad.
Insert the HEX codes into the spaces between the quote marks and after the # sign for
each line after you see the code, BGCOLOR= “#          ”. Insert the estimated wavelength
of the color of light into the line below. The example below has six colors represented.

When finished, save the file by clicking, File, Save As. You must give the file a new
name, and be sure to type the extension, .htm afterwards. Example: myspectrum.htm. To
view your webpage, open up Internet Explorer, and click File, Open, Browse to find your
newly-created webpage.
Your webpage will resemble this:

Christine Schnittka

Assessment Strategies
Throughout this lesson, there are discussion questions posed for informal assessment of
students’ understanding. For a more formal assessment, see the document, Color
Comprehension Check. The final projects: the spectra photograph, the color analysis
worksheet, and the spectra webpage, also assess students’ understanding. You can
challenge your students to make a spectra webpage with more of a color gradient, say
with twelve different colors represented instead of six. Students will have to create more
lines of text in the HTML source code of specweb.htm, but they can copy and paste them.
If they’re successful, the webpage will look something like this:

Christine Schnittka

Additional Resources

RGB Java applet

Filtering colors out of white light

Color HEX codes

HEX to RGB and RGB to HEX

History of Neon Signs

Lots of good stuff

Info on the eye

History of optics

Spectral colors


Using a CD-ROM to see the spectrum

Make permanent rainbows

Wavelength of colors

Christine Schnittka

Approximate RGB values for wavelength

The Science of Color (additive and subtractive)

Additive colors Java applet

Additive and Subtractive applet

Subtractive colors Java applet


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