ch31_jnlr

Christian Huygens was a Dutch scientist in the late 1600's. He cam eup with an idea about waves. -His **principle** states that wave fronts are made up of smaller wave fronts. -As a wave front spreads out, it will look as it forms a plane, and less like it forms a curve. Huygens Principle can demonstrate the lwas of reflection adn refraction. ~If you place something like a ruler into water horizontally, straight waves will be made. If there is a small opening ahead, less of the wave will get through and the wave will become curved. The bending of a wave by means other than reflection or refraction. -The opening is wide compared to the wavelegnth--->spreading effect is small -The opening is smaller compared to the wavelegnth--->spreading effect is larger (ALL WAVES) Light passing through... a large opening--->sharp shaddow small opening--->fuzzy shaddow (diffracion occurs in all shaddows, even the sharpest can be blurred at the edges) //diffraction fringes- wehn light has one color, its a border around the edge of the shaddow caused by diffraction. [in white light, the fringe will merge to make a blury fringe at the end of the shaddow]//
 * b Chapter 31- Diffraction and Interference**
 * 31.1 Huygens' Principle**
 * 31.2 Diffraction**

Two sets of waves crossing eachothers paths can cause an interference pattern (wave effects are either increased, decreased, or neutralized). -crests overlap other crest--->effects combine=constructive interference -crests overlap other trough---> effects combine= destructive interference __ripple tanks-__ tanks of water where water waves are produced in carefully controlled conditions. when two sources are placed side by side... -the greater the frequency, the closer the waves. __monochromatic light__-light of a single color By Thomas Young in 1801, discovered that when monochromatic light is directed through two closely placed pineholes, fringes of of brightness and darkness are produced on a screen behind. The fringes result from light waves from both holes arriving from crest to crest. The dark areas result from light waves arriving trough to crest.--->demonstrating Hiygens Principle __diffraction grating-__ a multitude of closely spaced parallel slits. -most commonly seen in reflective materials Interference fringes can be produced be light reflection from two surfaces close together. -monochromatic light shined on two plates of glass that are one atop the other, will show dark bands. ~this resuts from the interferencebetween the waves reflected from the glass on the top and bottom surfaces of the air space between the plates. EX: a good use is testing of precision lenses. if the tested lens is placed on flat piece of glass and illuminated with monochromatic light, light/dark fringes are seen. -if there are irregular fringes there is an irregular surface. __iridescence-__ when colors are produced by the interference of light waves of mixed frequencies in thin films. -In something such as a film, incoherent**- light emitted by a common lamp. It has many phases of vobrations and frequencies. The light is chaotic and and rampant, it spreads out after a sort distance. laser-light amplification by stimulated emission of radiation. A light wave emitted from one atom stimulates the emission of light from a neighboring atom so the crests of each wave concides. -when light falls on a hologram, it is diffracted by the fringed pattern to produce wav fronts identical on form to the origional wave fronts reflected by the object.
 * 31.3 Interference**
 * 31.4 Young's Interference Experiment**
 * 31.5 Single- Color Interference from Thin Films**
 * 31.6 Iridescence of Thin Films**
 * 31.7 Laser Light
 * choerent**- a beam of light that has the same freqency, phase, and direction. there are no interference between waves. It is produced by a laser.
 * 31.8 The Hologram** a three dimensional picture of an object that contains an interference pattern ...