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