Reflections and SuperpositionContents:

•Reflections•Why they occur•Preventing•Types•Angles

•Superposition•Definition•Constructive/Destructive

Why Reflections Occur

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Reflections occur at any abrupt change in mediumDemo wave device - Fixed, Free, change

Why Reflections Occur

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Reflections occur at any abrupt change in mediumLight Reflecting

Why Reflections Occur

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Reflections occur at any abrupt change in mediumSound Reflecting

Why Reflections OccurReflections occur at any abrupt change in medium

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More examples: Waves off islands - Polynesian navigators Long Distance telephone calls:

Your phone

Their phone

US Phone system

Cable or satellite

French phone system

Preventing reflectionsReflections occur at any abrupt change in medium

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2 ways to prevent reflection:Make there be no change in mediumMake the change less abrupt (i.e. gradual)

8 ohms

4ohms

Your Stereo Your Speaker

8 ohms

4 ohms

Impedance Transformer

Preventing reflectionsReflections occur at any abrupt change in medium2 ways to prevent reflection:

Make there be no change in mediumMake the change less abrupt (i.e. gradual)

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More examples: -Wave device demo Coatings on telescope lensesAcoustic impedance transformer (demo)Bells on horns

An anechoic room

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Wave energy is dissipatedNote lack of reflective surfacesVoice of tour guide

Types of reflections:

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Fixed ends invert: (demo) Free ends do not: (demo)

Angle of incidence = angle of reflection:

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Note unusual measure of angleRight angle corners(prisms and Mt. St. Helens center)Demo - laser/physics grooming mirror/Wash. Sq. Mall/sound in corners

Angle of incidence = angle of reflection:

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Smooth surfaces vs. rough

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Every object reflects some lightNot always a mirror

Field Trip time:Hallway/commons

Lecture hall