Presentation on theme: "14.4 Color and Polarization pp. 543 - 548 Mr. Richter."— Presentation transcript:
14.4 Color and Polarization pp. 543 - 548 Mr. Richter
Agenda (Today and Tomorrow Review Homework Introduction to Color Notes: Color Color and Light Color and Pigment Polarization
Objectives: We Will Be Able To… Recognize how additive colors effect the color of light. Recognize how pigments affect the color of reflected light. Explain how linearly polarized light is formed and detected.
Warm-Up: Leaves are green. What makes them green? That is, why do we perceive them to be green? Discuss at your table and we will discuss as a class in a few minutes.
Introduction to Color The color of an object appears different depending on the lighting conditions. Think about what you look like under a black light. Or some jerk’s sunglasses. The color of an object depends on which wavelengths of light shine on the object, and which wavelengths are reflected.
Color Remember, white (visible) light is a combination or red, orange, yellow, green, blue and violet. These colors each have different wavelengths red = ~700 nm violet = ~400nm When light hits an object, some wavelengths are absorbed, and some are reflected.
Color An object will appear to be the color of the light that it reflects. Green leaves appear green because they absorb all wavelengths of light except green, which they reflect. If a red light shines on a green leaf, what color will the leaf appear to be? Black!
Color Green objects only reflect green light. When white light shines on green objects (white light contains green), green light is reflected When red light shines on green objects (red light contains no green), the light is absorbed, and the object appears black. What color does the leaf appear if green light shines on it? Green, of course!
A prism breaks up light into six (or seven) distinct colors. These beams of light cannot be further broken up, but they can be put back together. If we add two colors of pure light together, we can create new colors. This is not the same as mixing pigments!
Color and Light The three primary colors of light are red green and blue When two of these colors combine, they create a secondary color red + green = yellow red + blue = magenta blue + green = cyan
Color and Light (fun facts) The human eye can only detect the primary colors of light: red, blue and green. Everything else is a combination of those colors. Visual screens like monitors and TVs only have red, blue and green pixels. The brightness of each pixel contributes to the overall picture color.
Color and Light: Your Turn A substance is known to reflect green and blue light. What color would it appear to be when it is illuminated by the following colors of light? 1.white light 2.blue light 3.magenta light 4.red light 1) cyan, 2) blue, 3) blue, 4) black
Warm-Up If pure yellow light shines on a magenta t-shirt, what color will the t-shirt appear to an observer? Yellow light = green + red light Magenta = reflects red + blue Yellow shining on magenta reflects only red light
Agenda Warm-Up Upcoming Schedule/Exam Notes: Color and Pigment Polarization
Upcoming Schedule Today: Finish 14.4 Tomorrow: Ch. 14 Review Friday: Ch. 14 Test (No Quarterly Exam) Next Week: Refraction!
When colors of light are mixed, they are additive. Yellow light (red + green) mixed with blue light all combine to form white light. When colors of pigment are mixed, the result is different. Yellow pigment mixed with cyan pigment creates green. Why?
Color and Pigment When colors of pigment mix, they are subtractive. Each pigment (like a paint color) only reflects certain colors of light. The more pigments are mixed, the less light is reflected back.
Color and Pigment The primary pigment colors are: cyan yellow magenta Just like a printer cartridge. All other pigments are formed from combinations of these pigments.
Light from most sources has electric and magnetic fields that oscillate at all random angles. Vertical, horizontal,, etc. This light is said to be unpolarized.
Polarization Light is polarized when the all of the electromagnetic waves are transmitted at the same angle. Everything is aligned. The vibrations of the electric and magnetic fields are parallel to each other.
Polarization Light can be polarized in two ways: Transmission: a polarizer (good word!) allows only waves of a certain angle to pass through. Kind of like a picket fence. Reflection: most waves of light bouncing off of a surface are polarized parallel to that surface Like glare off of glass or other shiny objects.
Polarization: Applications Most light we see that is polarized due to reflection is horizontally polarized. Parallel to snow covered ground, car hoods, lakes, etc. Glasses and goggles are polarized vertically to block this glare. Like adding a horizontal picket fence.
Wrap-Up: Did we meet our objectives? Recognize how additive colors effect the color of light. Recognize how pigments affect the color of reflected light. Explain how linearly polarized light is formed.
Homework p. 548 #1-4 p. 552 #37-39, 41 Chapter 14 Test Friday