chapter 16 light
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Chapter 16 Light. 16.1 Illumination. The electromagnetic spectrum Includes more that just Visible light. Visible light is electromagnetic radiation with wavelengths from 400 to 700 nm. An electromagnetic wave is A transverse wave consisting Of oscillating electric and - PowerPoint PPT PresentationTRANSCRIPT
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Visible light is electromagnetic radiation with wavelengths
from 400 to 700 nm.
The electromagnetic spectrumIncludes more that just
Visible light.
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An electromagnetic wave isA transverse wave consisting
Of oscillating electric andMagnetic fields at rightAngles to each other.
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Electromagnetic waves varyDepending on frequency and wavelength, this is
Called the spectrum.
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Classification Applications
Radio Waves AM or FM radio and television
Microwaves Radar, Microwaves ovens
Infrared Waves Heat, photography, physical therapy
Visible Light Seeing, photography
Ultraviolet Light Sterilization
X-Rays Medical Exams
Gamma Rays Cancer Treatment
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All electromagnetic wavesMove at the speed of light.
c = f λ
C = 2.998 X 108
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The AM radio band extends From 5.4 X 105 Hz to
1.7 X 106 Hz. What are the Longest and shortest wavelengths
In this frequency range?
560 m and 180 m
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A luminous body is one thatEmits light waves.
An illuminated body simply Reflects light waves produced
From an outside source.
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Waves can be approximated As rays for easier drawing
And visualization.
Brightness decreases by the Square of the distance from
The source. This is called the inverse
Square law.
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The Candela is the SI base unitOf luminous intensity,
It is also called a candle power.
Luminous flux (P) is the rate at Which light is emitted from a
Source.
A lumen is a unit of Luminous flux.
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Illuminance (E) is the rate at whichLight falls on a surface.
Lux is a unit of illuminance,Lumens per square meter.
E = P4πd2
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What is the illumination onYour desktop if it is lighted by A 1750 lm lamp that is 2.5m
Above your desk?
E = 22.3 lx
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In 1665, Francesco Grimaldi Observed that the edges of a
Shadow are not perfectly sharp.
He also noted that the shadowWas bordered by colored bands.
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Grimaldi recognized this Phenomenon as diffraction,
Which is the bending of lightAround a barrier.
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Additive primary colors produceWhite light when combined.
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Subtractive primary colorsFilter out all light when combined.
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A primary color is a color from Which all other colors
Can be derived.
A secondary color formed by A pair of two primary colors.
A complementary color is two Colors of light which when added
Together produce white light.
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A dye is a molecule that absorbsSome light wavelengths andReflects or transmits others.
A pigment is a colored materialThat absorbs certain colors And reflects or transmits
Other colors.
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A primary pigment is a pigment That absorbs only one color
from white light.
A secondary pigment is a pigment that absorbs two primary Colors from white light.
Thin-film interference is light Interference caused by reflection From the front and back surface
Of a thin layer of liquid.
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Color
All visible colored light together produce white light (ex. sunlight).
• White is not a single color, but a combination of all colors.
• White objects reflect all colors.
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Black is not a single color – it is the absence of light.
• Black objects absorb all frequencies of light.
• They reflect only enough light so that you can see them.
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• An object’s color depends on which light frequencies are reflected and which are absorbed.
– Ex: A blue shirt appears blue because it absorbs all colors EXCEPT blue. It reflects the blue back to our eyes.
– Ex: A plant leaf is green because it absorbs all the colors BUT green to use for photosynthesis.
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Linear polarization is the Alignment of electromagneticWaves in such a way that the Vibrations of the electric fields
In each of the waves are Parallel to each other.
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