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INTERACTIONS OF WAVES Interference Refraction Diffraction

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Presentation on theme: "INTERACTIONS OF WAVES Interference Refraction Diffraction"— Presentation transcript:

1 INTERACTIONS OF WAVES Interference Refraction Diffraction
Doppler Effect Polarization

2 Reflection When an object or wave hits a surface through which it cannot, pass it bounces back. This is called reflection.

3 Law of Reflection This law states the angle of reflection is congruent to the angle of incidence.

4 Reflection Waves bounce back at a boundary.
The reflected wave is exactly like the incident wave. At a fixed boundary , the wave will reflect but it will turn upside down.

5 Fixed boundary

6 INTERFERENCE when 2 or more waves meet while traveling in the same medium (overlapping waves) the NET displacement (amplitude) is the sum of the amplitude of the waves Constructive or destructive interference Creates standing waves & beats

7 CONSTRUCTIVE INTERFERENCE
larger displacement (larger amplitude) crest overlaps crest  or tough overlaps trough

8 DESTRUCTIVE INTERFERENCE
smaller displacement (smaller amplitude) crest overlaps trough  displacement/ amplitude is reduced crest cancels trough 

9 BEATS: INTERFERENCE Overlapping waves of different f (frequencies)
In music interference creates “beats” (changes in loudness & softness) Wave 1 (red) and Wave 2 (blue) combine to form beat pattern (in green) High amplitude = LOUD Low amplitude = soft

10 STANDING WAVES: INTERFERENCE
when two overlapping waves traveling in opposite direction have the same frequency Points that have no displacement  NODES Large, moving displacements  ANTINODES (max. amplitudes) String instruments

11 CONSTRUCTIVE INTERFERENCE
Resonance When an object vibration at a particular frequency Seen in musical instruments, especially strings Sympathetic resonance When one vibrating object induces a vibration in another object Soldiers do not walk in formation across bridges Tacoma Narrows Bridge

12 REFRACTION when a wave changes direction (& speed) as it passes from one medium into another Refraction depends upon density of medium Greater densities mean greater refraction (i.e. more bending)

13 REFRACTION What happens to the ray as it enters the water with less of an angle?

14 REFRACTION IN NATURE Wave speed depends on the medium
Click on picture for internet animation

15 DIFFRACTION when a wave bends around an edge or spreads through an opening familiar examples: sound waves (speakers in a room) and water waves (breaker opening in harbors) the amount of diffraction increases with increasing λ

16 DIFFRACTION Being able to hear around corners
Happens with light waves too (affects photography)

17 How is DIFFRACTION different from REFRACTION?
Diffraction = wave bends around an edge Refraction = wave bends because it changes from 1 medium to another (and, therefore, changes speed).

18 DOPPLER EFFECT the shift in frequency of wave when a wave source and an observer are moving relative to each other A stationary bug producing disturbances in water A• • B A bug moving to the right and producing disturbances A• •B Notice how waves near B are “compressed” → ƒ higher Waves “leaving” A are “expanded” → ƒ lower apparent increase in ƒ for observers as the source approaches/ moves closer to observer apparent decrease in ƒ for observers as the source recedes / moves away from observer

19 DOPPLER EFFECT: SOUND Longer λ for observers as train leaves
Shorter λ for observers as train approaches

20 DOPPLER EFFECT: LIGHT Longer λ for observers as train leaves = light shifts RED Shorter λ for observers as train gets closer = Light shifts BLUE

21 POLARIZATION when the displacement of a transverse wave is in a specific orientation or direction  familiar example: polarized sunglasses polarized materials only allow waves that correspond to a special direction to pass through

22 PRACTICE Reflection Refraction Diffraction Interference Polarization
Word bank: Reflection Refraction Diffraction Interference Polarization Doppler Effect

23 PRACTICE Reflection Refraction Diffraction Interference Polarization
Word bank: Reflection Refraction Diffraction Interference Polarization Doppler Effect

24 INTERFERENCE RESOURCES
for applets. for applet. To change frequencies, etc., enter new value, and RETURN. To pause, left click. For Harmonics & Beats applets link to The Soundry Sound Lab (left sidebar)


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