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Transcript of Light &ColorLight &ColorLight &ColorLight &Color.
Light & Color
Light is an electromagnetic wave
• Electric field waves perpendicular to Magnetic field waves.
• Both are perpendicular to direction wave is traveling.
• This makes it a transverse wave.
Electromagnetic Spectrum (longest wavelength to shortest wavelength)
1. Radio and TV 2. Microwaves 3. Infrared 4. Visible
5. Ultraviolet 6. X-rays 7. Gamma Rays
• Violet light has a wavelength of about 400 nm• Red light has a wavelength of about 700 nm
Different wavelengths of light have different colors.
Color Spectrum (from longest to shortest wavelengths)
ROYGBIV 1. Red
2. Orange
3. Yellow
4. Green
5. Blue
6. Indigo (Now
a Goner!)
7. Violet
Galileo was first to try to measure speed of light.
• Before Galileo, everyone thought light had no speed
• Galileo first to hypothesize light had a finite speed
• Used lanterns with shutters as first experiment.
• Decided light was too fast to measure.
Speed of light, wavelength of light, frequency of light relationship
c = f• c = speed of light (m/s)• = wavelength of light (m)• f = frequency of light (Hz)
The speed of light is a set value
C = 300,000,000 m/s = 3.00 x 108 m/s = 300,000 km/s = 186,000 mi./s
Transparent Objects• Allow light to pass through them
undisturbed.• No trouble identifying objects
behind transparent objects.• Examples: glass, transparencies,
clear liquids
Translucent Objects• Light can pass through, but not
clearly.• Reflect some light, but also allow
some light to pass through (transmit)
• Examples: tissue paper, lampshades, frosted light bulbs...
Opaque Objects
• Materials which do not allow light to pass through.
• Only reflect light.• Examples: bricks, doors,
people...
Luminous
• Objects which create light are said to be Luminous
• Examples: Sun, stars, light bulbs
ILLUMINATED
• Objects which reflect light• These objects do not create their own light• examples: Moon, planets, desk, whiteboard,
people...
Color of Light
Making Colors by Addition of Light
Primary Light Colors
• Three colors:• Red, blue, green• Combinations of any of these two produce
secondary colors, all three colors added together make white light
• These are illumines and create their own light
Light Color addition
Red + Blue = Magenta
Blue + Green = Cyan
Green + Red = Yellow
Venn Diagram of Color
Light color addition (cont.)
• Color monitors and TV screens use this principle
• By varying the intensity of the three colors, any pixel can have any color possible.
Making Colors by Subtraction
Pigments
Primary Pigments
• These are opaque and luminous• Compose of magenta, cyan, and
Yellow• Absorb and reflect light rather
then illuminate it.• Mixtures of paints from these
primary color pigments can produce any color imaginable.
Venn Diagram of Pigment
WHAT WE SEE?Reflected v. Absorbed
We can only see reflected colors
ALL OTHER COLORS ARE ABSORBED
BEHAVIOR OF LIGHT:
REFRACTION
BEHAVIOR OF LIGHT:
REFLECTION
GIVING LIGHT DIRECTION:
POLARIZATION
Polarization of Light• Unpolarized light vibrates in all directions
in the xyz plane.• In this illustration the electric field (E) is
vibrating on the y-axis, and the Magnetic field (B) is vibrating on the z-axis. The wave is traveling along the x-axis.
Polarization (cont.)
• Polarizers are made of long strands of molecules that are all aligned parallel to each other.
• Look at blue in the illustration.
Polarizers will only allow light that is vibrating parallel to the direction the
polarizer is ligned up. Polarizers will not allow light to pass through if it is vibrating
perpendicular to it.