Wave behavior

1. Refraction   is the  "bending of waves" .
• A wave passing from one medium to another medium of different density changes its speed causing the wave to bend
• The speed of the wave is greatest in the less dense medium

2. Reflection

"bouncing back" of a wave

• Laws of Reflection - The angle of incidence equals the angle of reflection (or it can be stated q₁ = q₂) ; the incident wave, the reflected wave, and the normal all lie in the same plane
• Angle of incidence and angle of reflection are always drawn relative to the normal.

• Example of reflection - echo
• Go to this website to see waves reflected
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2. Interference    - result of the superposition of two or more waves
• Superposition Principle - when two waves are in the same place at the same time, the displacement caused by the waves is the algebraic sum of the two waves.  Two situations can occur.  There can be constructive or destructive interference.  Lets examine adding the following two waves.

Two waves of equal amplitude but slightly different frequencies interfere destructively and constructively. The result is an alternation of loudness called a beat.

 In Constructive interference, the signs of the waves are the same and the resulting wave is greater in amplitude than the individual waves.  In destructive interference, the signs of the waves are the different and the resulting wave is smaller in amplitude than the individual waves.

Please use the following applets to watch constructive and destructive interference.

http://users.erols.com/renau/wave_interference.html

http://webphysics.ph.msstate.edu/jc/library/15-11/index.html

this applet is particularly great if your sound card is working:

http://library.thinkquest.org/19537/java/Beats.html

Diffraction The ability of waves to bend around the edge of an obstacle in their path is called diffraction. 

Please go to this web site to read about diffraction.

http://open.dtcc.cc.nc.us/opticianry/oph141/diffract.htm

When a pebble is dropped into a pool of still water, a circular wave is generated that travels away from the point where the pebble entered. The farther the wave goes from the point where the pebble entered the water, the straighter the wave becomes.

But if a barrier with a small opening stops the wave, the small part of the wave that passes through the barrier becomes circular again -- as if the pebble had been dropped into the water at that point.

We say that the wave has bent around the barrier, or that it has changed directions: Where the wave was traveling in a straight line before passing the barrier, it has now 'bent' or changed directions after passing the barrier.

DIFFRACTION of a wave is the bending or redirection of the travel of the wave when it passes a barrier without changing the medium in which the wave is traveling.