2. NSF North Mississippi GK-82 Today’s Topics Light –What is it? –Visible Spectrum Why do we see color? Why are objects specific colors? http://priory.net/~fyamasaki/images/rainbow_sun.jpg

3. NSF North Mississippi GK-83 Why is light important? Almost everything in nature depends on light for life: –Plants use light to make food as a byproduct oxygen is produced. –Humans use light to see, make X-Rays, as electricity (solar energy), and many other things. http://home.howstuffworks.com/irrigation1.htm

4. NSF North Mississippi GK-84 What is Light? Light is a form of energy that sometimes behaves like waves. –All waves have a wavelength which is the distance between one point on one wave and the same point on the next wave.

5. NSF North Mississippi GK-85 Wavelengths of Light Different wavelengths of light include radio waves, ultraviolet rays, and X-rays. These wavelengths of light and others make up a spectrum.

6. NSF North Mississippi GK-86 Visible Spectrum Shorter wavelengths have more energy than longer ones. Sunlight, which is the most important source of light, contains all of the electromagnetic spectrum. –Humans can only see a small range of light called the visible spectrum.

7. NSF North Mississippi GK-87 Visible Spectrum The visible spectrum contains seven colors: violet, indigo, blue, green, yellow, orange, and red. The seven colors of the visible spectrum are the seven colors in a rainbow. http://ldt.stanford.edu/ldt1999/Students/tita/mjrproj/color/wavereview.html

8. NSF North Mississippi GK-88 Colors in a Rainbow How can I remember the seven colors of the rainbow? ROY G BIVROY G BIVROY G BIVROY G BIV EDED RANGERANGE ELLOWELLOW REENREEN LUELUE NDIGONDIGO IOLETIOLET

9. NSF North Mississippi GK-89 Colors in a Rainbow Another way to remember: Make a sentence. –Example: Rainbows Over Your Garden Bring Ideal Vegetables.

10. NSF North Mississippi GK-810 White Light White light contains all colors of the rainbow.

11. NSF North Mississippi GK-811 Why do we see color? When our eyes see different wavelengths of light in the visible spectrum, we see colors. How do humans see color? –What we actually see is the light an object reflects or in some cases the light an object produces. –Our eyes absorb the wavelengths of light in the visible spectrum. Then, turn these wavelengths into signals our brains can understand. The brain interrupts these signals as color images. http://www.astronomynotes.com/light/colorswvl.gif

12. NSF North Mississippi GK-812 Why are objects a specific color? The grass appears green, because the leaves reflect green light. The leaves do not absorb (soak up) this wavelength of light and reflect it back (like a mirror), so we see the grass as green. On the other hand a green stoplight appears green because it produces green light.

13. NSF North Mississippi GK-813 Sun’s Rays (White Light) Green Wavelength of light Absorbs all other colors

14. NSF North Mississippi GK-814 White and Black Color White Color –When you see white, all of the wavelengths of light (all colors) are being reflected back at you. Black Color –When you see black, all of the wavelengths of light are absorbed and no light is reflected back at you.

15. NSF North Mississippi GK-815 Review What is light? –Light is a form of energy that sometimes behaves like waves. What is a wavelength? –Distance from crest to crest or trough to trough.

16. NSF North Mississippi GK-816 Review What are the colors of a rainbow? ROY G BIVROY G BIVROY G BIVROY G BIV EDED RANGERANGE ELLOWELLOW REENREEN LUELUE NDIGONDIGO IOLETIOLET

17. NSF North Mississippi GK-817 Review Why do we see color? –You see different wavelengths of light as color. http://ldt.stanford.edu/ldt1999/Students/tita/mjrproj/color/wavereview.html

18. NSF North Mississippi GK-818 References Barkstrom, Bruce R. August 18, 2005. What Wavelength Goes With a Color?. 2005 August 18..http://eosweb.larc.nasa.gov/EDDOCS/Wavelengths_for_Colors.h tml Brown, Earle B. “Light.” The World Book Encyclopedia. 1986 ed. Gourdeau, Justine. November 3, 2003. Clouds and Particles: Basics – Rainbows. 2005 August 18..http://www.atmosphere.mpg.de/enid/f962eee1b06705f8f51b4d b2901f8668,55a304092d09/3__Sun_and_clouds/- _Rainbow_tj.html McGrath, Susan. Fun With Physics. Washington, D.C.: The National Geographic Society, 1986. Wyszecki, Gunter. “Color.” The World Book Encyclopedia. 1986 ed.