Color

How do we see color?

• Different colors have different energies– Low energies = red – High energies = violet

• Photoreceptors : cells on retina of eye– Cells receive light and release a chemicals to brain

• 2 Types:1. Cone cells see color • 3 types: Red, Green, and Blue (RGB)

2. Rod cells see brightness• Only see black, white, and gray• Work at low light levels

– Why most things look black or white at night

Additive Color (RGB)

• 3 colors are red, green, and blue (RGB)• Start with a black background• Add lights to add color• Equal amounts of all three get white color• Different amounts for any color– R&B make magenta (purple)– R&G make yellow– G&B make cyan (sea green)

Subtractive Color (CMYK):

• Light reflected off pigments on a white background

• 3 subtractive primary colors – yellow, magenta, and cyan (CMY)– K = black

• Pigment of the object affects the light that is absorbed:

• Cyan absorbs R and reflects B&G• Magenta absorbs G and reflects R&B• Yellow absorbs B and reflects R&G

• What you see is light being reflected– Absorb all light look black– Reflect all light look white

• Example: Green Plant– Green is reflected while all other colors are

absorbed– Photosynthesis • Plants need sunlight, H20 and CO2

• Takes place in chlorophyll • Plants need all lights but not green• If only a green light is shined onto a plant, the plant will

die since no energy is absorbed

Why is the Sky Blue?

• Shortest l colors (BIV) get trapped and scattered in upper atmosphere (atm)

Sunsets/Sunrises

• Light rays have a longer path to travel in atm– Shortest l reflected off (GBIV)– Longest l come through (ROY) • Lights are scattered in atm

Works Cited

• Blue Sky - Red Sunset. N.d. Photograph. Scifun.orgWeb. 29 May 2012. http://scifun.chem.wisc.edu/HomeExpts/BlueSky.html .

• Hsu Ph.D., Tom. Foundations of Physical Science. 1st ed. Peabody: Cambridge Physics Outlet, 2002. 242-248. Print.

• Microsoft Office PowerPoint ClipArt. 2000.• Why is the Sky Blue?. 2010. Photograph.

EnchantedLearning.comWeb. 29 May 2012. http://www.enchantedlearning.com/subjects/astronomy/planets/earth/Skyblue.shtml .