Todays Topics

1
(No Transcript)
2
Todays Topics

• Light
• What is it?
• Visible Spectrum
• Why do we see color?
• Why are objects specific colors?

http//priory.net/fyamasaki/images/rainbow_sun.jp
g
3
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.

4
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
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
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
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.

8
Colors in a Rainbow

• How can I remember the seven colors of the
  rainbow?

ROY G BIV
RANGE
NDIGO
REEN
LUE
IOLET
ED
ELLOW
9
Colors in a Rainbow

• Another way to remember Make a sentence.
• Example Rainbows Over Your Garden Bring Ideal
  Vegetables.

10
White Light

• White light contains all colors of the rainbow.

11
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.

12
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
Suns Rays (White Light)
Green Wavelength of light
Absorbs all other colors
14
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
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
Review

• What are the colors of a rainbow?

ROY G BIV
RANGE
ELLOW
NDIGO
REEN
LUE
IOLET
ED
17
Review

• Why do we see color?
• You see different wavelengths of light as color.

http//ldt.stanford.edu/ldt1999/Students/tita/mjrp
roj/color/wavereview.html
18
References

• Barkstrom, Bruce R. August 18, 2005. What
  Wavelength Goes With a Color?. 2005 August 18.
  r_Colors.html.
• Brown, Earle B. Light. The World Book
  Encyclopedia. 1986 ed.
• Gourdeau, Justine. November 3, 2003. Clouds and
  Particles Basics Rainbows. 2005 August 18.
  8f51b4db2901f8668,55a304092d09/3__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.