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4-1 Radiant Energy
Waves
Light travels in Waves similar to ocean waves Light waves are electromagnetic and consist of an
electric and magnetic fields oscillating at right angles to each other in the direction of motion.
Wavelength – distance between crests Amplitude – height of the wave measured from the
origin to its crest or peakBrightness
Frequency – tells how fast a wave oscillates The number of times a wave completes an up and down
cycleMeasured in cycles per second s-1 = 1/s = hertz = Hz
Light moves in space at a constant speed. c = 3.00 x 108 m/sBecause of this, there is a relationship between
wavelength and frequency.Shorter the wavelength, the faster the oscillation
c = x = c/
Practice Problem
Calculate the wavelength of a radio wave with a frequency of 93.1 x 106 s-1
= c/ = 3.00 x 108 m/s / 93.1 x 106 s-1
= 3.22 m
Electromagnetic Spectrum
We see light in the visible spectrum Each color that we see has a different wavelengths.
400 nm (violet) – 700 nm ( red) Visible light is a very small portion of the
electromagnetic spectrum. Much of the spectrum is below and above the
Visible portion 10-11m – 101m
Beyond red is the infrared portion. This is also called radiant heat Used in microwaves, radio
waves, tv waves
Beyond violet is the ultraviolet radiation (UV) Responsible for sunburns
and skin cancer. X-rays are even shorter in
wavelength
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