1. Physics 1 H Created by Stephanie Ingle
Light and Color
Physics 1 H
Created by Stephanie Ingle

2. Light Light is a transverse wave.
Light waves are electromagnetic waves--which means that they do NOT need a medium to travel.
Light waves behave like other waves and have the same characteristics such as amplitude, frequency, and wavelength.

3. Characteristics of Light
Intensity (brightness) -- represented by amplitude
Color -- determined by frequency
Wave speed - depends on the medium
Light waves as well as ALL Electromagnetic waves travel with a speed of 3.0 x 108 m/s in a vacuum.

4. Luminous Flux (P)
Luminous flux is the rate at which light energy is emitted from the source.
Equivalent to Power
Measured in lumens (lm)

5. Luminous Intensity (I)
The amount of light (luminous flux) that falls on one square meter at a distance of 1 meter from the source.
Equivalent to Intensity at r = 1 m
Measured in candelas (cd)
I = P/4 or cd = lm/4

6. Luminous vs Illuminated
a body that emits light
has luminous flux
Illuminated
a body that reflects light
no luminous flux
does not emit light of its own

7. Illuminance (E) E = P/(4r2) Amount of light that falls on a surface
Intensity of light at any given distance from source
measured in lux
lux = lumen/m2 r
bulb
E = P/(4r2)

8. Other Electromagnetic Waves
Radio
Microwaves
Infrared
Ultraviolet
X-rays
Gamma Rays
Radar
All of these follow the same rules as Light and travel at the same speed.
Light is simply a way of referring to the visible portion of the electromagnetic spectrum.

9. Characteristics of Electromagnetic Waves
Made up of 2 components
electric field & magnetic field
The electric and magnetic fields are perpendicular to each other.
A changing electric field will create a magnetic field and a changing magnetic field will create an electric field; therefore the wave propagates itself through space without need of a medium.

10. Light and Color There are 3 primary colors of light RED, GREEN, & BLUE
When these colors of light are mixed… White Light is produced
This process is called color addition

11. Color Addition (Light)
Red + Green = Yellow
Red + Blue = Magenta
Blue + Green = Cyan
Red + Green + Blue = White
Yellow, Magenta, and Cyan are called the secondary colors of light because they are produced using 2 of the primary colors.

12. Pigments Pigments work on the principle of color subtraction.
The light we see is reflected light.
A pigment of a certain color will reflect only that color of light and absorb all other frequencies.
Example: A blue shirt will reflect incident blue light and absorb red and green.

13. Primary Pigments
The primary pigment colors are magenta, cyan, and yellow because they absorb only one frequency of color.
Yellow absorbs blue and reflects red and green.
Cyan absorbs red and reflects blue and green.
Magenta absorbs green and reflects red and blue

14. Color Subtraction (Pigments)
Mixing pigments means that you will see only the color that both colors reflect. Red, Blue and Green are secondary pigments because they absorb 2 colors.
Magenta + Yellow = Red
Cyan + Magenta = Blue
Yellow + Cyan = Green

15. Black and White
White light is the mixture of all frequencies (colors) of light.
A white surface will reflect all frequencies (colors) of light.
Black is not a color!
Black is the absence of any light.
A black surface will absorb all incident light and reflect none.