Transcription of UNIT 2 THE ELECTROMAGNETIC SPECTRUM
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UNIT 2 THE ELECTROMAGNETIC SPECTRUM
Like expanding ripples in a pond after a pebblehas been tossed in, ELECTROMAGNETIC radiationtravels across space in the form of waves. Thesewaves travel at the speed of light 300,000 kilo-meters per second. Their wavelengths, the dis-tance from wave crest to wave crest, vary fromthousands of kilometers across (in the case ofthe longest radio waves) to fractions of ananometer, in the cases of the smallest x-raysand gamma rays. ELECTROMAGNETIC radiation has properties of bothwaves and particles. What we detect depends on themethod we use to study it. The beautiful colors thatappear in a soap film or in the dispersion of lightfrom a diamond are best described as waves. Thelight that strikes a solar cell to produce an electriccurrent is best described as a particle. Whendescribed as particles, individual packets of electro-magnetic energy are called photons.
700 nanometers and 0.1 cm. (Nano means one billionth. Thus 700 nanometers is a distance equal to 700 billionths or 7 x 10-7 meter.) Visible light is a very narrow band of radiation ranging from 400 to 700 nanometers. For comparison, it would take 50 visible light waves arranged end to end to span the thickness of a sheet of household plastic wrap.
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