Color

1. Color

2. Selective Reflection: When we perceive an object to be a particular color, we actually are receiving only one particular color of light in our eye. Ex: A banana looks yellow because it reflects only yellow light. It absorbs all the other colors.

3. ROY G BIV White light Another discovery by Isaac Newton White Light: White light is not a distinct color. Instead, white light is the combination of all the other colors.

4. Newton’s Prism Work • Before Newton, it was thought that the prism added color to the light… • Newton tested this idea by breaking the light into the spectrum, then again dividing a single color of the spectrum with another prism to test if it would again “add” color to the light. • Once he discovered it did not, he reached the conclusion that the original white light had contained all of the colors that were seen coming from the prism.

5. Black: When an object appears black, it means that all colors ( frequencies) of light are being absorbed by that object. None are being reflected. Often, black objects are hotter because they are absorbing more light/energy.

6. What? • White light is made up of? • Lots of different speed light • Red and Green Light • All the colors of the rainbow • Mostly blue

7. Lights: All of the previous assumes that the objects are illuminated by white light. However, many sources aren’t purely white. Ex: fluorescent lights emphasize the blue frequencies, incandescent lights may appear yellowish...

8. reflected absorbed If a rose were illuminated with a red light, you would see the red rose as? Red Black

9. reflected absorbed If a rose were illuminated with a red light, you would see the green leaves? Red Black Green

10. Selective Transmission: Not all objects reflect light (opaque), some let light pass through them ( transparent). In this case, if a transparent object looks blue, this means that all colors except blue are being absorbed.

11. Mixing Colored Light: The sun is a pretty good source of white light. Below is a curve showing the relative proportions of the visible light it produces: R O Y G B I V Infra-red ultraviolet

12. The colors of white light are often simplified into three components: Red, Green, Blue These are often called the additive primary colors

13. In a TV, these three colors are used to create all the various images you view. Look closely at your TV screen and you’ll see….

14. Yellow Magenta Cyan (light blue) White When the three additive primary colors of light are mixed, the following results are obtained:

15. If a golf ball were illuminated with RBG lamps, could you explain the following result?

16. Pigments: If you have ever used play-dough, you’ve noticed that if you mix R,B,G colors of clay, you don’t get white as a result! This is an example of mixing pigments, not light. Different results are obvious here.

17. In a lump of clay, you see the light that is reflected (leftover), after the rest has been absorbed. For this reason, in painting and printing, magenta, cyan, and yellow are called the subtractive primary colors. They are often referred to loosely as red, yellow, and blue.

18. In a color ink jet printer, you often have a color cartridge with cyan, magneta, and yellow colors. (CMY) These small dots are used to create any image needed. An additional black cartridge is often included.

19. The violet/blue light is reflected/scattered the most, so we see those colors. Our eye cones aren’t as sensitive to voilet, so we see a predominantly blue sky.

20. Why are Sunsets Red: Q: If the sky is blue here on Earth, why do we see sunsets as orange/red?

21. Air molecules A: In the previous description, we said the atmosphere scatters or reflects the blue light the most. This leaves the red light to continue through the atmosphere.

22. When the sun is low on the horizon, the light is passing through a lot of the atmosphere. The blue is scattered (subtracted), and orange/red light is leftover.

23. The blueness of the sky, or the redness of a sunset depends on many factors like humidity and air pollution. In 1883, Mt. Krakatoa erupted. The addition of many small particles produced more spectacular sunsets/rises around the world.

24. The Scream The famous painting, The Scream, was painted in 1893 by Edvard Munch. In his diary he wrote that it was inspired by a blood red sunset. Courtesy of Nicole H.

25. Why is the Ocean Green/Blue? Again, the answer has to do with absorption and transmission. Water resonates or vibrates at infrared and red frequencies. This means it absorbs the red light. If the red light is taken away, the remaining green & blue light ( cyan ), remains!

26. Once again, the exact color of the water depends on many factors.

27. Review Question: Q: Why does the blood of an injured deep sea diver look greenish-black when photographed with natural light, but red when a flash is used?

28. Deep in the water, most of the red light has already been absorbed. Thus, with no red light reflecting off the normally red blood, it looks black. With a flashbulb, there is a new source of red light to be reflected!