1. Interference & Wave Behavior Physics – 5th 6wks

2. Interference
Interference - When two or more waves overlap and combine to form a new wave.
Constructive Interference is when the crest of one wave overlaps the crest of another, adding their amplitudes together.
Destructive Interference however is when The high part (or crest) of one wave simply fills in the low part (or trough) of another wave, and they cancel each other out.

3. Interference
In Longitudinal waves, constructive interference occurs when two or more compressions coincide.
Destructive interference in longitudinal waves occurs when a compression and a rarefaction meet.
Slinky interference
interference on surface of water
Film of Interference Patterns

4. Interference areas of destructive interference
(the arrows on the right)
areas of constructive
interference
(the arrows on the left)

5. Wave Behavior: When Waves Meet Obstacles
Waves can do 4 different things when they hit an obstacle: reflect, refract, diffract, or be absorbed.
Plane waves – waves that move
Perpendicular to the wave fronts.
Circular waves – waves that radiate
Outward from the center.

6. Wave Behavior: Refraction
Recall that a wave’s speed depends upon the medium that it is traveling through.
When a wave passes from one medium to another – such as when light waves move from air to water – it changes speed.
Refraction – the bending of a wave caused by a change in its speed as it moves from one medium to another.
The unique amount that a material causes a wave to refract is known as the Index of Refraction
The greater the change in speed, the more the wave bends.

7. Constructive vs. Destructive Interference

8. Wave Behavior: Diffraction
Diffraction – the bending of waves around a barrier.
Diffraction occurs when an object causes a wave to change direction and bend around it.
After the waves pass through a narrow opening they spread out.
Waves tend to spread into shadow regions.

9. Diffraction… continued
If the wavelength is about the same size (or larger) than an object or opening that it encounters, the shadow is soon filled in. – Waves with larger wavelengths can more easily diffract around or through obstacles.
If a wavelength is less than the width of the object it is passing through or the object it is encountering, a sharper, more focused shadow is formed – waves with smaller wavelengths tend to be blocked

10. Diffraction… continuedAM FM
Diffraction through a small opening turns plane waves into circular waves, thus causing them to radiate outward.
FM radio waves have smaller wavelengths than do AM radio waves, and don’t diffract as much around buildings.
AM radio waves are picked up further because of this.
Sound waves are much longer than light waves, and thus diffract more. This is why you can hear someone around a corner but not see them.
Its diffraction and I know it

11. Wave Behavior: Absorption & Reflection
Depending upon what material a wave strikes, they may be absorbed.
Absorption – the result of a wave striking an object and disappearing.
Reflection – the result of a wave striking an object and bouncing off of it.
Echoes and images in mirrors are the result of wave reflection.
All types of waves – including sound, water, and light waves – can be reflected.

12. Wave Damping
Damping – the decrease in the amplitude of a wave over time.
Damping is the result of friction reducing the energy of a wave.
Note: as damping occurs, frequency and wavelength remain the same if no other energy is added

13. The Law of Reflection
The light coming into a surface is the incident ray
The light coming off of a surface is the reflected ray
An imaginary line that is perpendicular to the surface that is
being struck by the wave is called the Normal
The angle between the incident ray and the normal (˂i) is
equal to the angle between the normal and the reflected ray
(˂r) ii

14. The Law of Reflection
If a ray of light could be observed reflecting off of a flat mirror, then it would behave in the manner illustrated above.
Under ideal situations, the angle which light strikes an object is equal to the angle which it bounces off of an object.
This is known as The Law of Reflection
Although the most commonly mentioned example of the law has to do with light waves striking a surface, it must be noted that the law applies to all types of waves (sound waves, etc.) ii

15. Law of Reflection continued
The Law of Reflection is Always Observed (regardless of the orientation of the surface)

16. Law of Reflection: Smooth vs. Rough Surfaces
Most surfaces are not smooth, upon magnification even
seemingly smooth surfaces have undulations.
To the right is an image of copy paper under magnification
Reflecting off of a smooth surface is known as
Specular Reflection and can produce a crisp image due
to a concentrated bundle of light waves. (light off a mirror)
Reflecting off of a rough surface is known as Diffuse
Reflection and light waves will reflect in multiple directions (think
of light reflecting off of asphalt or paper)
Sound also obeys the Law of Reflection

17. Misc. Clips longitudinal wave in slinky slow mo
transverse wave in slinky in slo mo
Transverse vs Longitudinal Waves video
Refraction of Ocean Waves
Refraction of Sound Waves example
Water Droplet hitting water in slo mo
Mythbusters Rubens Tube
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Rubens Tube Journey Dont stop believin
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