DAY 75

Goal:

SWBAT write a sentence explaining how the combination of the indigo and orange filters creates red light.

WARM-UP

Color perception, like sound perception, is a complex subject involving the disciplines of psychology, physiology, biology, chemistry and physics. When you look at an object and perceive a distinct color, you are not necessarily seeing a single frequency of light.

1. When you see indigo, which two colors are being combined to create that color?

2. When you see orange, which two colors are being combined to create that color?

Hint: You can use the phet RGB color simulator from yesterday to create those colors, and answer the above questions LINK

CLASSWORK

Review from yesterday:

Color Addition Rules

These demonstrations with the color box illustrate that red light and green light add together to produce yellow (Y) light. Red light and blue light add together to produce magenta (M) light. Green light and blue light add together to produce cyan (C) light. And finally, red light and green light and blue light add together to produce white light. This is sometimes demonstrated by the following color equations and graphic:

R + G = Y

R + B = M

G + B = C

075A: Reading/Notes "Where Does Color Come From?"

The color of the objects that we see is largely due to the way those objects interact with light and ultimately reflect or transmit it to our eyes.
The color of an object is not actually within the object itself. The color is in the light that shines upon it and is ultimately reflected or transmitted to our eyes.
Visible light spectrum consists of a range of frequencies, each of which corresponds to a specific color.
When visible light strikes an object and a specific frequency becomes absorbed, that frequency of light will never make it to our eyes.
Any visible light that strikes the object and becomes reflected or transmitted to our eyes will contribute to the color appearance of that object.
So the color is not in the object itself, but in the light that strikes the object and ultimately reaches our eye.
The only role that the object plays is that it might contain atoms capable of selectively absorbing one or more frequencies of the visible light that shine upon it.
So if an object absorbs all of the frequencies of visible light except for the frequency associated with green light, then the object will appear green in the presence of ROYGBIV.
And if an object absorbs all of the frequencies of visible light except for the frequency associated with blue light, then the object will appear blue in the presence of ROYGBIV.
Consider the two diagrams below. The diagrams depict a sheet of paper being illuminated with white light (ROYGBIV). The papers are impregnated with a chemical capable of absorbing one or more of the colors of white light. Such chemicals that are capable of selectively absorbing one or more frequency of white light are known as pigments. In Example A, the pigment in the sheet of paper is capable of absorbing red, orange, yellow, blue, indigo and violet. In Example B, the pigment in the sheet of paper is capable of absorbing orange, yellow, green, blue, indigo and violet. In each case, whatever color is not absorbed is reflected.

1. Check your understanding of these principles by determining which color(s) of light are reflected by the paper and what color the paper will appear to an observer.

What about TRANSPARENT materials?

Transparent materials are materials that allow one or more of the frequencies of visible light to be transmitted through them; whatever color(s) is/are not transmitted by such objects, are typically absorbed by them. The appearance of a transparent object is dependent upon what color(s) of light is/are incident upon the object and what color(s) of light is/are transmitted through the object.

2. Express your understanding of this principle by filling in the blanks in the following diagrams.

3. The diagrams depict a sheet of paper being illuminated with white light (ROYGBIV). The papers are impregnated with a chemical capable of absorbing one or more of the colors of white light. In each case, determine which color(s) of light are reflected by the paper and what color the paper will appear to an observer.

4. The appearance of a transparent object is dependent upon which color(s) of light is/are incident upon the object and which color(s) of light is/are transmitted through the object. Express your understanding of this principle by determining which color(s) of light will be transmitted and the color that the paper will appear to an observer.

075B: Color Filters Simulator

Key Question: how can you combine two or more filters to create a specific color? (think of our in class demo - how did orange and indigo filters transmit red light?)

Handout: LINK

Interactive: LINK

HOMEWORK

Complete 075B.

write a sentence explaining how the combination of the indigo and orange filters creates red light.

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