electromagnetic waves and color
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Electromagnetic Waves and Color. Physics Ms. Shaver. Color. Color is the perceptual quality of light. The human eye can distinguish almost ten million colors. Types of Materials. Transparent light passes thru without scattering. Translucent - PowerPoint PPT PresentationTRANSCRIPT
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Electromagnetic Waves and Color
PhysicsMs. Shaver
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Color
•Color is the perceptual quality of light.
• The human eye
can distinguish almost ten million colors.
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Types of Materials
Transparent light passes thru without scattering TranslucentLight passes thru diffusely (scatters in all directions)
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Color comes to our eyes from objects due to:
• Emission• Reflection• Transmission• Interference• Dispersion• Scattering
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Emission: the object itself is a source of light.
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Reflection: certain
frequencies are
reflected from the object,
others are absorbed.
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A particular material absorbs the light frequency that matches the frequency at which electrons in the atoms of that material vibrate.
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• The energy of the frequency absorbed turns to heat.
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Transmission: certain frequencies are transmitted through the object, others
are absorbed.
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Scattering: the
reradiation of certain
frequencies of light, striking
small, suspended particles.
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Interference: constructive and destructive interference.
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Dispersion: the angular
separation of a light wave
during refraction.
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Why do we see the colors of the rainbow?
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Light and water paint the Rainbow in the sky
When raindrop A disperses light, only the red light exits at the correct angle to travel to the observer's eyes. The other colored beams exit at a lower angle, so the observer doesn't see them. The sunlight will hit all the surrounding raindrops in the same way, so they will all bounce red light onto the observer.
Raindrop B is much lower in the sky, so it doesn't bounce red light to the observer. At its height, the violet light exits at the correct angle to travel to the observer's eye. All the drops surrounding raindrop B bounce light in the same way. The raindrops in between A and B all bounce different colors of light to the observer, so the observer sees the full color spectrum.
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Why is the sky blue?
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Why the sky is blue
A clear cloudless day-time sky is blue because molecules in the air scatter blue light from the sun more than they scatter red light. When we look towards the sun at sunset, we see red and orange colors because the blue light has been scattered out and away from the line of sight.
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Why is the ocean sometimes blue, gray or
green?
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Ocean ColorThe red, orange, yellow, and green wavelengths of light are absorbed so that the remaining light we see is composed of the shorter wavelength blues and violets.
microscopic marine algae, called phytoplankton, have the capacity to absorb light in the blue and red region of the spectrum owing to specific pigments like chlorophyll. Accordingly, as the concentration of phytoplankton increases in the water, the color of the water shifts toward the green part of the spectrum.
Fine mineral particles like sediment absorb light in the blue part of the spectrum, causing the water to turn brownish in case of massive sediment load.
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Primary Colors of Light
http://photographycourse.net/wp-content/uploads/2008/03/rgb_illumination-300x225.jpg
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Primary Colors of Light: Red, Green, Blue-combine to white
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Secondary colors of Light:cyan, magenta, and yellow-
also combine to white.
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• A complementary color is formed by subtracting a primary color from white light.
• Every secondary color is the complement of a primary color.
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If a blue and yellow flashlight strike a white object at the same time, what color will the object
appear?
Blue + yellow = white since yellow light contains green and red.
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If red is subtracted from white, what color remains?
Cyan
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What color will a blue ball appear if a red light only
strikes it and why?
=>
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Color of light is an additive process with respect to
frequency. Why?
• The primary colors when added together give white light.
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Additive Color of Light Mixing Applications
• Movie film • Slide projector • Television and computer displays
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Primary Colors of Pigment(Cyan, Yellow, Magenta combine
to give Black color pigment)
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Notes
• The primary colors of pigment are the secondary colors of light and vice versa.
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When magenta and cyan pigments are mixed what
color results?
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Pigment is a subtractive color process. Why?
• Colors are formed by absorbing (taking away) certain frequencies from white light.
• The absence of a reflected light wave appears as black color.
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Applications: painting, printing, etc.
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Example: What makes a leaf green
• A green leaf reflects green light• A green leaf has chlorophyll that
absorbs red and blue light