MOD 5  LECTURE 3                       WAVE - MATTER INTERACTIONS

In this lecture you will:

WAVE - MATTER INTERACTIONS OVERVIEW

Here is a good source of information on the science of sound.  We will study only a few of them in conjunction with what is happening to light in interference, reflection, refraction, diffraction, and reflection. At the end we will take up the doppler effect of both sound and light. 
http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html

Here is an overall view of the various areas of light and vision that are studied by science. We have already looked at quantum properties of light.  In this lecture we will look at interference. 
http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html

 
SUMMARY OF WAVE - MATTER INTERACTIONS
Type of waves Main interaction  SOUND LIGHT (EMS)
INTERFERENCE Run into each other acoustics (loud/soft) holograms (bright/dark)
REFLECTION Hit and bounce off surfaces acoustics: echoes and reverberations mirrors, colors, shiny and matte
REFRACTION Enter clear materials and bends rumble of thunderstorms lenses, diamonds, rainbows
DIFFRACTION Bend around solid or little slit how we hear around a post slits, rainbow effect on CD or DVD

 
INTERFERENCE: IN GENERAL
When waves run into each other, they can amplify or cancel each other out

if the waves are synchronized, crest to crest, trough to trough, then they amplify
if the waves are crest to trough, they cancel
- in between they cancel or amplify to varying degrees
 

SOUND INTERFERENCE
EXAMPLE: in badly constructed amphitheaters there are seats where the sound comes together and cancels.  This is also the reason that the speakers of "surround sound" systems have to be carefully placed.
 

What we hear is softer or louder 

HOW WE HEAR SOUND WAVES
1. Something vibrates and creates a sound wave.
2. The sound wave travels to the ear and is collect by the outer ear.
3. The sound wave then moves into the ear canal.
4. At the end of the ear canal, the sound waves bump against the eardrum.
5. The ear drum vibrates with these sound waves.
6. The vibration moves tiny bones in the middle ear.
7. These bones carry vibrations into the inner ear to a fluid filled tube called the cochlea.
8. The fluid inside vibrates a series of tiny hairs called cilia, which are attached to auditory nerves.
9. The movement of cilia stimulates nerve cells, and  send signals to the brain via the auditory nerve.
10. The brain processes these signals into the sounds we hear

http://www.learningthroughlistening.org/Listening-A-Powerful-Skill/Listening-and-Learning/Benefits-
of-Teaching-Listening/93/

LIGHT INTERFERENCE
"The wave properties of light lead to interference, but certain conditions of coherence must be met for these interference effects to be readily visible. "
http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html

http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html
SINGLE AND DOUBLE SLIT INTERFERENCE
Here is a very good visual explanation for light interference.  Light waves enter at all positions of the slit and as they move forward they cancel or amplify to varying degrees causing the pattern seen on the wall or screen. 

Interference is what we see as alternate dimmer or brighter spots in a row

Double slit interference pattern
HOLOGRAM CREATION USING INTERFERENCE
"Holography is "lensless photography" in which an image is captured not as an image focused on film, but as an interference pattern on the film. 
 a
SUMMARY OF EFFECTS
loud and soft areas of sound in concerts sound interference
bright or dim areas lined up in a row on a surface light interference
holograms  light interference using lasers
 b