Light
“Then Jesus spoke to them again, saying, 'I am the light of the world. He who follows Me shall not
walk in darkness, but have the light of life.'” John 8:12
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electromagnetic waves exist with an enormous range of frequencies
--> remember that frequency is the number of vibrations per second of a wave
this continuous range of frequencies is know as the electromagnetic spectrum
the longer wavelength/lower frequency regions are located at the far left of the spectrum and
the shorter wavelength/higher frequency regions are on the far right:
Visible light spectrum
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our eyes are sensitive only to a very narrow band ranging from 700 nanometers (nm) to 400
nm
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called the visible light spectrum because this is the range that humans see; these wavelengths
stimulate the retina in our eyes, specifically the cone cells
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include the colors red/orange/yellow/green/blue/indigo/violet ROYGBIV
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each individual wavelength within the spectrum of visible light represents a particular color
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white light shining through a prism will be separated into its different wavelengths
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when all the wavelengths of the visible light spectrum strike your eye at the same time, white
is perceived; visible light is the mix of ROYGBIV
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there is NOT a wavelength for white because white is a combination of all colors of the
visible spectrum
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absence of all the wavelengths of the visible light spectrum = black; dark room means no
wavelengths of visible light are striking your retina --> cone cells of the retina can still
perceive dark v. light
Check Your Understanding
1. A light wave is an electromagnetic wave that has both an electric and magnetic component associated with it. Electromagnetic
waves are often distinguished from mechanical waves. The distinction is based on the fact that electromagnetic waves can travel
through a region void of matter and mechanical waves cannot.
2. Consider the electromagnetic spectrum as you answer these three questions.
a. Which region of the electromagnetic spectrum has the highest frequency?
b. Which region of the electromagnetic spectrum has the longest wavelength?
c. Which region of the electromagnetic spectrum will travel with the fastest speed?
See