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Chapter 12 Section 4. Wave Interactions. Wave Interference. It’s impossible for two material objects to occupy the same space at the same time . Waves on the other hand are able to occupy the same space at the same time. Superposition.
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Chapter 12 Section 4 Wave Interactions
Wave Interference • It’s impossible for two material objects to occupy the same space at the same time. • Waves on the other hand are able to occupy the same space at the same time.
Superposition • Superposition – The ability for a wave to occupy the same space at the same time. • Superposition is possible for all forms of waves: • Sound • Water • Light
Constructive Interference • Constructive Interference – Interference in which individual displacements on the same side of the equilibrium position are added together to form a resultant wave. • When the two waves meet, they form a larger amplitude wave. Once they pass through one another, they return to their original amplitude.
Destructive Interference • Destructive Interference – Interference in which individual displacements on opposite sides of the equilibrium position are added together to form a resultant wave. • When the two waves meet, they form a smaller amplitude wave or even cancel out. Once they pass through one another, they return to their original amplitude.
Constructive vs. Destructive Interference • Superposition of Waves Animation • http://www.acs.psu.edu/drussell/Demos/superposition/superposition.html
Interferences In Waves • The method of summing the displacements of waves is known as the Superposition Principle. • This principle only holds true for small waves • Superposition principle is valid for both transverse and longitudinal waves.
Wave Reflection • At a free boundary, waves are reflected back to the source and the amplitude is unchanged. • At a fixed boundary, waves are reflected and inverted back to the source with the amplitude unchanged but upside down.
Standing Waves • Standing Wave – Wave pattern that results when two waves of the same frequency, wavelength, and amplitude travel in opposite directions and interfere. • Node – Point in a standing wave that always undergoes complete destructive interference and therefore is stationary. • Antinode – Point in a standing wave, halfway between two nodes, at which the largest amplitude occurs.
Standing Waves Explained • Standing Waves are formed when both ends of a string, rope or spring, are fixed at both ends and the waves reflect on both ends. • The incident and reflected waves combine according to superposition principle. • As long as the frequency of the waves remains constant a standing wave will form.
Doppler Effect? • Your standing on a street and some driving by honks the horn, you will notice the pitch of the horn change. • The pitch gets higher as the car comes closer. • Once the car passes, the pitch will drop. • The pitch depends on the frequency of the wave.
Doppler Effect Animation • http://www.astro.ubc.ca/~scharein/a311/Sim.html#Doppler
Doppler Effect of Light • Doppler effect can happen for light waves as well.
Doppler Effect • Doppler Effect – Frequency shift that is the result of relative motion between the course and an observer. • When an object moves, it effects the frequency of the wave that is being emitted. • Doppler effect occurs for all types of waves.