Class11 - Superposition of Waves "Super" means...

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2/1/12 Oregon State University PH 202, Lecture 11 1 Superposition of Waves “Super” means “over.” Supervisor Superstructure Superimpose So when we superimpose waves, we position one wave over another —combining them. But we can describe waves mathematically, as functions. And to superimpose two functions, we simply add them. Example : Superimpose these two lines. y 1 = x + 2 y 2 = 2 x – 3 y = y 1 + y 2 = 3 x – 1
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2/1/12 Oregon State University PH 202, Lecture 11 2 Functions can be superimposed not only in space (on a graph) but also in time. What does this mean physically? For example, what is happening when two waves arrive at the same place ( x ) at the same time ( t )? Look first at a simple wave example (Figure 16.3 in the textbook): (Also, look at Stop To Think 16.1 on your own.)
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2/1/12 Oregon State University PH 202, Lecture 11 3 This same process works for adding sinusoidal wave functions. Example : Look at two identical sinusoidal sound waves as they meet in time and space. With sound waves, keep in mind, it’s generally not displacement of particles we’re commonly graphing. It’s the pressure, P , of the medium (air or water, etc.). So the amplitude, A , has units of pressure here. P 1 = A cos[(2 π / λ ) x – (2 π f ) t ] P 2 = A cos[(2 π / λ ) x – (2 π f ) t ] P = P 1 + P 2 = 2 A cos[(2 π / λ ) x – (2 π f ) t ]
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2/1/12 Oregon State University PH 202, Lecture 11
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Class11 - Superposition of Waves "Super" means...

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