Ch27_RabinR

= Chapter 27 - Light Waves and Colortoc =

Lesson 1 Summary
How Do We Know Light is a Wave? (Method 4) Light exhibits characteristics of both waves and particles. Light exhibits certain behaviors that are characteristic of any waves. This includes reflection, refraction, diffraction, interference, and the Doppler Effect.
 * What are the wave-like behaviors of light?**

Reflection - bouncing off of an obstacle Follows the LAW OF REFLECTION when bouncing off surfaces -- he angle at which the wave approaches a flat reflecting surface is equal to the angle at which the wave leaves the surface

Refraction - when a wavefront crosses the boundary between two media, the direction that the wavefront is moving undergoes a sudden change; the path is "bent" 1) Direction of "bending" is dependent upon the relative speed of the two media (A wave will bend one way when it passes from a medium in which it travels slowly into a medium in which it travels fast; and if moving from a fast medium to a slow medium, the wavefront will bend in the opposite direction) 2) Amount of bending is dependent upon the actual speeds of the two media on each side of the boundar

Diffraction - change in direction of waves as they pass through an opening or around an obstacle in their path Light diffracts obstacles, can be observed by the extreme fuzziness of the edges of shadows (Interference effects occur due to the diffraction of light around different sides of the object, causing the shadow of the object to be fuzzy)

Wave interference - phenomenon that occurs when two waves meet while traveling along the same medium. The interference of waves causes the medium to take on a shape that results from the net effect of the two individual waves upon the particles of the medium.
 * What is two point source interference?**

Constructive interference - occurs at any location along the medium where the two interfering waves have a displacement in the same direction Destructive interference - occurs at any location along the medium where the two interfering waves have a displacement in the opposite direction

Two-Point Source Interference Patterns

Crests - thick lines Troughs - thin lines
 * Depicts an interference pattern produced by two periodic disturbances**

Constructive interference - thick line meet a thick line/thin line meets a thin line --> FORMS AN ANTINODE (Red dot)

Destructive interference - thick line meets a thin line --> FORMS A NODE (Blue dot)

The lines antinodes are located along are called antinodal lines while the lines nodes are located along are called nodal lines. Two-Point Source Interference Pattern - the pattern of alternating nodal and antinodal lines

Change in wavelength (or frequency) of the source - alter the number of lines in the pattern and alter the proximity or closeness of the lines Increase in frequency - result in more lines per centimeter and a smaller distance between each consecutive line Decrease in frequency - result in fewer lines per centimeter and a greater distance between each consecutive line Sources are moved further apart - more lines produced per centimeter and lines move closer together

Two-Point Light Interference Patterns Constructive Interference - (crest meeting crest or trough meeting trough) two waves act to reinforce one another and produce a "super light wave" Destructive Interference - (crest meeting trough) two waves act to destroy each other and produce no light


 * What is thin film interference?**