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Superposition and Spectra. Physics 11. Multiple waves. We now understand the very basics of waves but reality usually does not involve one just one wave. Multiple radio stations transmitting into the room Waves on the surface of a pool as people are jumping in
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Superposition and Spectra Physics 11
Multiple waves • We now understand the very basics of waves but reality usually does not involve one just one wave. • Multiple radio stations transmitting into the room • Waves on the surface of a pool as people are jumping in • White light (it is a composite of waves in the EM spectrum) • So what doe these waves look like?
Superposition • Superimpose two waves together. • Add them together • For each value of x, add the value of each wave to get a resultant
Real Waves are Superpositions • This means that real waves have a number of waves adding together to make them up. • Each part having a different wavelength • The wavelengths that are used to construct a complex wave are referred to as a “Spectrum” (plural, ‘Spectra’)
Spectrum Graphs • Real waves are composed of many components • To keep track of what wavelengths are used, a simple chart is often made. • Consider the emission spectrum of Hydrogen • It tells us what wavelengths are present, indicating the wavelength qualitatively with the color of light Hydrogen
Intensity Spectra • Spectra plots can include information about amplitude at each wavelength • Consider these plots made for common ‘white light’ sources
Interference: An Effect of Superposition • Interference is a word used to describe superposition of two waves with the same wavelength. • Constructive interference: • Waves add together to give a greater amplitude • Destructive interference: • Waves add together, one cancels the amplitude of the other.
Interference: An Effect of Super Position • Traveling waves superimpose and then travel through each other. • Constructive (antinode)
Interference: An Effect of Super Position • Traveling waves superimpose and then travel through each other. • Destructive (node)
Superposition – A Process • ID all maxes, mins and zeros • At each point IDed in 1, determine the sum of the waveforms at this point; place a mark at the point that shows the sum the two waveforms • Connect the dots with a smooth curve
Beat Frequency • When two sounds have slightly different frequencies, a beat frequency can be observed • This is a pulsation of the sound and the greater the difference between the frequencies, the higher the beat frequency • http://www.youtube.com/watch?v=5hxQDAmdNWE