In this lecture you will learn about:
|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|
|WAVES HIT AND BOUNCE OFF OF SOLID, NON
|"Light incident upon a surface will in
general be partially reflected and partially transmitted as a refracted
ray. The angle relationships for both reflection and refraction can be
derived from Fermat's principle. The fact that the angle of incidence is
equal to the angle of reflection is sometimes called the "law of reflection".
When a ray of light hits a solid, non transparent surface of material it can be absorbed and/or reflected
Most matter reflects light. "COLOR" is what happens when waves are reflected. The color of an item is the wavelength that is reflected back to the eye. So black is the absorption of all colors, white the reflection of all colors.
The energy of the absorbed wavelengths are converted to kinetic energy of the absorbing atoms. So black garments in winter heat up faster than white ones because black absorbs all light wavelengths (and IR). In summer heat white garments reflect all waves and so dont absorb much and dont heat up.
|Objects are "shiny" or "matte" depending on how smooth or rough the surface of the item is. A smooth surface reflects the light in nice parallel lines (in phase) while the rough surface reflects at odd angles which interfere and CANCEL the light waves (out of phase).|
film interference is a combination of reflection and interference.
It is responsible for the rainbow effect of soap bubbles and oil
"Constructive and destructive interference of light waves is also the reason why thin films, such as soap bubbles, show colorful patterns. This is known as thin film interference, because it is the interference of light waves reflecting off the top surface of a film with the waves reflecting from the bottom surface. To obtain a nice colored pattern, the thickness of the film has to be on the order of the wavelength of light.
Consider the case of a thin film of oil floating on water. Thin film interference can take place if these two light waves interfere constructively:
1. the light from the air reflecting off the top surface
2. the light traveling from the air, through the oil, reflecting off the bottom surface, traveling back through the oil and out into the air again. "
Iridescence is caused by multiple reflections from multi-layered, semi-transparent surfaces in which phase shift and interference of the reflections modulates the incident light (by amplifying or attenuating some frequencies more than others). This process is the functional analog of selective wavelength attenuation as seen with the Fabry-Pérot interferometer."
|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|
|colors||light reflection and absorption|
|shiny or matte||light reflection and interference|
|soap bubbles and oil spill rainbows||light reflection and interference|
|iridescence||reflection and interference|