Electromagnetic Waves and Color
Color Color is the perceptual quality of light. Color is the perceptual quality of light. The human eye can distinguish almost ten million colors. The human eye can distinguish almost ten million colors.
Cornea – outer coating Iris and pupil – opening that allows light to travel into eye Lens – focuses light Retina (Cones and rods) – focused light collected
Types of Materials Transparent Translucent
Types of Materials Transparent – material transmits light – most of the light that strikes it pass through it Transparent – material transmits light – most of the light that strikes it pass through it Translucent – scatters light (seeing through a material, but objects you see through it do not look clear or distinct Translucent – scatters light (seeing through a material, but objects you see through it do not look clear or distinct Opaque – absorbs or reflects all of the light that strikes it Opaque – absorbs or reflects all of the light that strikes it
Color comes to our eyes from objects due to: Emission Emission Reflection Reflection Transmission Transmission Interference Interference Dispersion Dispersion Scattering Scattering
Emission: the object itself is a source of light.
Reflection: certain frequencies are reflected from the object, others are absorbed.
A particular material absorbs the light frequency that matches the frequency at which electrons in the atoms of that material vibrate. A particular material absorbs the light frequency that matches the frequency at which electrons in the atoms of that material vibrate. The energy of the frequency absorbed turns to heat. The energy of the frequency absorbed turns to heat.
Transmission: certain frequencies are transmitted through the object, others are absorbed.
Scattering: the redirecting of certain frequencies of light, striking small, suspended particles.
Why is the sky blue?
Scattering Redirected as it passes through a medium Redirected as it passes through a medium Why the sky is blue or red sometimes? Why the sky is blue or red sometimes? Small particles in atmosphere scatter shorter wavelength (blue light) more than longer wavelengths. Small particles in atmosphere scatter shorter wavelength (blue light) more than longer wavelengths. At sunrise/sunset most blue, green, and some yellow light is scattered and only that reaches your eye is red and orange At sunrise/sunset most blue, green, and some yellow light is scattered and only that reaches your eye is red and orange During the daytime, blue light scatters in all direction more than other light During the daytime, blue light scatters in all direction more than other light
Interference: constructive and destructive interference.
Why do we see the colors of the rainbow?
Dispersion: the angular separation of a light wave during refraction.
Prism – Dispersion
Why is the ocean sometimes blue, gray or green?
Primary Colors of Light
Primary Colors of Light: Red, Green, Blue-combine to white
Secondary colors of Light: cyan, magenta, and yellow- also combine to white.
A complementary color is formed by subtracting a primary color from white light. A complementary color is formed by subtracting a primary color from white light. Every secondary color is the complement of a primary color. Every secondary color is the complement of a primary color.
The Colors of Objects The Colors of Objects The color of any object depends on what the object is made of and on the color of light that strikes the object. The color of any object depends on what the object is made of and on the color of light that strikes the object. Sunlight contains all the colors of the visible spectrum Sunlight contains all the colors of the visible spectrum Blue shirts – absorbs all colors except for blue Blue shirts – absorbs all colors except for blue Red shirts – absorbs all colors except for red Red shirts – absorbs all colors except for red
If a blue and yellow flashlight strike a white object at the same time, what color will the object appear? ANS: White
If red is subtracted from white, what color remains? ANS: Cyan
What color will a blue ball appear if a red light only strikes it and why? =>
Color of light is an additive process with respect to frequency. Why? The primary colors when added together give white light. The primary colors when added together give white light.
Additive Color of Light Mixing Applications Movie film Movie film Slide projector Slide projector Television and computer displays Television and computer displays
Primary Colors of Pigment (Cyan, Yellow, Magenta combine to give Black color pigment)
Notes Pigment – material that absorbs some colors of light and reflects other colors Pigment – material that absorbs some colors of light and reflects other colors The primary colors of pigment are the secondary colors of light and vice versa. The primary colors of pigment are the secondary colors of light and vice versa.
When magenta and cyan pigments are mixed what color results? ANS: Blue
Pigment is a subtractive color process. Why? Colors are formed by absorbing (taking away) certain frequencies from white light. Colors are formed by absorbing (taking away) certain frequencies from white light. The absence of a reflected light wave appears as black color. The absence of a reflected light wave appears as black color.
Applications: painting, printing, etc.