Download 3×10 8 m/s

Chapter 25: Light
Are you color coordinated?
California Standards
4. Waves have characteristic properties that do
not depend on the type of wave. As a basis for
understanding this concept:

4c. Students know how to solve problems involving
wavelength, frequency, and wave speed.

4e. Students know radio waves, light, and X-rays are
different wavelength bands in the spectrum of
electromagnetic waves whose speed in a vacuum is
approximately 3×108 m/s (186,000 miles/second).
25.1
Light Fundamentals
25.1 Objectives
Recognize that light is the visible portion of an
entire range of electromagnetic frequencies.
Describe the ray model of light.
Solve problems involving the speed of light.
Define luminous intensity, luminous flux, and
illuminance.
Solve illumination problems.
What is Light?
What is light? Light is a form of energy. Light is the range
of frequencies of electromagnetic waves that stimulates
the retina of the eye. Light has wavelengths from about
400 nm (4.00 x 10-7 m) to 700 nm (7.00 x 10-7 m). Light
behaves like both a particle and a wave.
What is Light?
Light Frequencies
The electromagnetic wave spectrum covers Radio,
microwaves, infrared (IR), ultraviolet (UV), X-rays,
Gamma Rays, and visible light. Visible light is a very
small portion of the entire scale.
Light Frequencies
It is now known that the ranges of X-rays and Gamma
Rays largely overlap. X-rays are emitted by electrons
outside the nucleus, while gamma rays are emitted by
the nucleus. All EM waves produce photon particles.
The Speed of Light
Light travels at the speed
of 299,792,458 m/s. We
use 3x108 m/s most
commonly for calculations.
The colors start at purple,
and move to blue, green,
yellow, orange, and red as
the wavelength is
increased.
This is how fast light travels from the sun to the earth (8 min 18 sec).
The Ray Model of Light
The Ray Model of Light
The ray model is a generic one. By using it we can
discuss the path taken by the light, without
committing ourselves to any specific description of
what it is that is moving along that path. We will
use the nice simple ray model for most of this book,
and with it we can analyze a great many devices
and phenomena.
Illumination
Luminance: Candela per square meter (cd/m2)
Luminous Intensity: Candela
Illuminance: Lux
(lm/sr; lumen/steradian)
(lm/m2)
Luminous Flux: Lumen (lm=cd
sr; candela × steradian)
Illumination
Luminous Flux:
Lumen (lm=cd
sr; candela × steradian).
L
Brightness 
2
4D
Brightness
Materials and Light
Opaque: No incident light is
transmitted.
Transparent: Transmits incident
light WITHOUT distortion.
Translucent: Transmits
incident light WITH
distortion.
Materials and Light
Opaque,
Transparent,
or
Translucent?
Light and Transparent Materials
Optical Illusions
Optical Illusions
Optical Illusions
Optical Illusions
Optical Illusions
Optical Illusions
Rainbows
Rainbows
Why is the Sky Blue & Sunset Pink?
25.2
Light and
Matter
25.2 Objectives
Explain the formation of color by light and by
pigments or dyes.
Explain the cause and give examples of
interference in thin films.
Describe methods of producing polarized
light.
Prisms
Prisms can be used to diffract light into all the colors
of the spectrum.
Mixing Colors
Why do the colors on the left combine to white
and those on the right combine to black?
Primary and Secondary Colors
Primary Color: Red, Green, Blue
Secondary Color: Colors formed from an
two primary colors: Yellow, Cyan, Magenta
Primary Pigment: Absorbs ONE
primary color.
Secondary Pigment: Absorbs TWO
primary colors.
Mixing Colors
Mixing Colors
Mr., You gonna catch Bat Man?
M
R
Y
G
C
B
M
Yellow-Green Sunlight Peak
Social Justice and Colors
White: The presence of all colors
of the spectrum
Clean, good, godly, spiritually pure, innocent, untainted,
morally beyond reproach. Star Wars, God vs. Satan,
The good guy wears white. Found in the light.
Black: The absence of all colors
of the spectrum
Dirty, evil, devilish, spiritually impure, guilty, tainted,
morally reproachable. Lost in the dark. The Bad guy wears black.
So, is the terminology racist?
Thin Layer Interference
Bubbles
Thin Layer Interference
Diesel Rainbow
Thin Layer Interference
Thin Layer Interference
Soap Bubble Refraction
Polarization
Polarization
Polarized Light + 3D Viewing