PHYS 1902 Lecture Notes - Lecture 4: Electromagnetic Spectrum, James Clerk Maxwell, Christiaan Huygens
15 Feb 2016
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Document Summary
Everyone knows what it is (but might have di culty de ning it!) Almost all the information we receive from the universe comes to us in the form of light (neutrinos the big exception) Light has a nite speed rst calculated by danish astronomer r mer in 1676 by timing the orbit of jupiter"s moon io he obtained 2 108m/s. Present day value 2. 99792458 108 m/s in our course 3 108m/s. Takes light about 1. 3 seconds to reach the moon from the earth, 8 minutes to reach the earth from the sun and about 5 hours for light to reach pluto from the sun. Think of a pebble dropped into a pond. Disturbance radiated, transported away from impact with water, energy in the mechanical motion of the water. Water does not move away from the impact the water only moves up and down, no translational motion. Waves are characterized by their amplitude, wavelength, speed, period and fre- quency.
