session 3 lecture outline
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SESSION 3 MODULE 3
Module 3 - Light
Module 3 is all about visible light how common sources produce
visible light, the common properties and
characteristics of light, And how the eye sees color
This session
FocusSpecial characteristic of
visible light: Color Visible light is the
narrow range of frequencies and wavelengths that can be seen by the human eye
The differences of wavelengths within this range are perceived as differences in color
Objectives Infer where colors
come from Relate color to
frequency and wavelength
Explain why objects appear in a particular color
Appreciate proper lighting in doing various activities.
KWL Chart
What I already
know about light
What I want to know
What I learned
•What did you see?• List the colors in order • How does the acronym ROY G BIV help you describe what you see?•Where could thave these colors come from?
Activity 1 What color goes with wavelength? Q1. Which color registers the highest
frequency? shortest wavelength? Q2. Which color registers the lowest frequency?
longest wavelength? Q3 What pattern do you notice about the
wavelength and frequency of the different colors?
Q4. When you take the product of wavelength and frequency, what do you get? What is the significance of this value?
Q5. What is a possible relationship between wavelength and frequency? How would you prove this relationship?
Q6. What can you say about the speed of the different colors of light in air?
Activity What color goes with wavelength?
Q1. Which color registers the highest frequency? shortest wavelength? Violet has the highest frequency and the shortest wavelength.
Q2. Which color registers the lowest frequency? Longest wavelength? Red has the lowest frequency and the longest wavelength.
Q3 What pattern do you notice about the wavelength and frequency of the different colors? Long wavelength colors have low frequencies.
Q4. What is a possible relationship between wavelength and frequency? How would you prove this relationship? Wavelength and frequency are inversely proportional. This can be proven by finding out whether the product wavelength x frequency would equal a constant.
Q5. When you take the product of wavelength and frequency, what do you get? What is the significance of this value? The product of wavelength and its corresponding frequency is very close to 3 x 108m/s, the speed of light in air.
The spectrum consists of color bands
the visible spectrum consists of color bands and therefore are identified by a range of wavelengths and frequencies to wit
Color Wavelength
λnm (10-9
m)
Frequency THz(1012 Hz
red 780 - 622 384 - 482
orange
622 - 597 482 - 503
yellow 597 - 577 503 - 520
green 577 - 492 520 - 610
blue 492 - 455 610 - 659
violet 455 - 390 659 - 769
Activity 2 Color of filters
Shine the flashlight on each filter and note the color of light projected on the screen
Q1. What is the color of the beam transmitted by the filter?
Q2. How does the color of the filter compare to the color it transmitted?
Q3. Write a general statement that describes the color of the filter and the color it transmits.
Activity 3 Color Mixing
Primary colors for light :
RED
GREEN
BLUE
Primary colors for paint pigments
Magenta Yellow cyan
http://users.halpc.org/~clement/Simulations/Mixing%20Colors/rgbColor.html
For light For paint pigments
Magenta + yellow = ____
Yellow + cyan = ______
Magenta + cyan = ______
Magneta + cyan + yellow = __________
Q4. Describe the color of the overlap:
Red + blue = ______
Blue + green = ________
Green + red = ________
Red + Green+ Blue = ____
Color Mixing
1. Click on the light bulb, paint can, and colored filter icons located in the toolbar on the left side to add them to the lab area. Clicking on an object in the scene removes it from the scene, while clicking on a projector specifies it as the recipient of the next light bulb that is selected. Clicking on the "Animate Beams" button activates the projectors and the user can directly observe how the selected items affect the color of the light beams as they travel through the scene.
http://www.cs.brown.edu/exploratories/freeSoftware/repository/edu/brown/cs/exploratories/applets/combinedColorMixing/combined_color_mixing_java_plugin.html)
Color that we see
Bulb Filter Paint Color we “see”:
Red Red RedGreen BlueMagentaCyanyellow
Green RedGreen BlueMagentaCyanyellow
Blue RedGreen BlueMagentaCyanyellow
Adding colors
White light can be split up to make separate colors. These colors can be added together again.
The primary colors of light are red, blue and green:Adding blue and
red makes magenta (purple)
Adding blue and green makes cyan
(light blue)
Adding all three makes white again
Adding red and green makes yellow
Using filters Filters can be used to “block” out different colors of
light:Red
Filter
Magenta Filter
Seeing color
The color an object appears depends on the colors of light it reflects.
For example, a red book only reflects red light:
White
lightOnly red light is reflected
A white hat would reflect all seven colours:
A pair of purple trousers would reflect purple light (and red and blue, as purple is made up of red and
blue):
Purple light
White
light
Using coloured light
If we look at a coloured object in coloured light we see something different. For example, consider a this pair of shirt and shorts:
White
light
Shorts look blue
Shirt looks red
In different colours of light they would look different:
Red
lightShirt looks red
Shorts look black
Blue
light
Shirt looks black
Shorts look blue
Generalizations
For light:
Primary colors: Red Green Blue
Red+ blue = magenta Blue + green = cyan Red + blue =yellow Red + blue + green =
white
For pigments
The color of a transparent object is the color it transmits
The color of an opaque material is the color it reflects
Evaluate
red
black
red
black
blue
green blue green
blackbluered