Light lecture outline

2. Focus
Special 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

3. 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 have these colors come from?

4.  Objective: In this activity, you should be
able to (1) design a color spectrum wheel
and (2) explore the special properties of
visible light
 Procedure:
 Part 1: Making the Spectrum Wheel
 Part 2: Characteristics of Light

5.  THz = terahertz = 1012
 Nm = nanometer = 10-9
 1 hertz = 1 / sec

6.  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. What do you notice about the product of
wavelength and frequency for each color?What is the
significance of this value?
 Q5. What is a possible relationship between
wavelength and frequency?What is your basis for
saying so?

7.  Q6. What can you say about the speed of the
different colors of light in air?
 Q7. Give a plausible explanation as to why white
light separate into different colors.
Color
Spectrum
Frequency
THz
Wavelength
nm
Wavelength x
Frequency
Red 422 700 m/s
Orange 484 620 8 m/s
Yellow 517 580 3 x 10 8 m/s
Green 566 530 3 x 10 8 m/s
Blue 638 470 3 x 10 8 m/s
Violet 744 400 3 x 10 8 m/s

8.  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.

9.  Q4. What do you notice about the product of wavelength
and frequency for each color? What is the significance of this
value?The product of wavelength and frequency for each color
are the same. It is very close to the speed of light in air.
 Q5. What is a possible relationship between wavelength
and frequency?What is your basis for saying so? Wavelength
and frequency are inversely proportional. As the frequency increases
wavelength decreases
 Q6. What can you say about the speed of the different
colors of light in air? The speed of the different colors of light
in air are the same.
 Q7. Give a plausible explanation as to why white light
separate into different colors. Answers may vary.

10.  the visible spectrum
consists of color
bands and
therefore are
identified by a
range of
wavelengths and
frequencies to wit
Color Wavelength
λ
nm (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

11.  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
www.phet.colorado.edu
http://lrmds.deped.gov.ph

12.  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 = ____

13.  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/exploratori
es/applets/combinedColorMixing/combined_color_mixing_java_plugin.html)

15. Bulb Filter Paint Color we “see”:
Red Red Red
Green
Blue
Magenta
Cyan
yellow
Green Red
Green
Blue
Magenta
Cyan
yellow
Blue Red
Green
Blue
Magenta
Cyan
yellow

16.  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

17.  Filters can be used to “block” out different colors of light:
Red Filter
Magenta
Filter

18.  The color an object appears depends on the colors of
light it reflects.
For example, a red book only reflects red light:
White
light
Only red light is
reflected

19. 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

20.  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

21.  In different colours of light they would look different:
Red
light
Shirt looks red
Shorts look black
Blue
light
Shirt looks black
Shorts look blue

22.  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

23. Evaluate