CH27

Chapter 27

= Lesson 1 (a-c) = How does light behave like a wave? Light does act like both a wave and a series of particles. For example, just like sound waves, light can undergo the doppler effect. The three big reasons are shown in reflection, refraction, and diffraction. In reflection, light can bounce off an object at the same angle as it approaches a mirrored surface. This is the "Law of Reflection" which is a characteristic of a stereotypical wave. In refraction, light changes direction when going from one medium to another. Again, this is done by waves. In diffraction, light goes around an obstacle leaving a fuzzy shadow around it, then having an interference on the opposite side. What is two-point interference? Wave interference is when two waves traveling in same medium come in contact with each other. It can be constructive, where two interfering go in the same direction to make a bigger trough, or destructive, where they go in opposite directions and partially or fully cancel each other out. Antinodes are when there is maximum displacement with constructive interference, and nodes are the opposite, they are the flatter parts. Patterns in waves can be altered by changing their frequencies or wavelengths and by changing the distances between the sources. With light, when a trough meets a trough or a crest meets a crest at constructive interference, there is brightness. When it is destructive, there is darkness. What is thin-film interference? Thin-film interference is when a light wave is reflected by the upper and lower boundaries of a thin film thus that there are two resulting waves that are close enough to have interference of their troughs and crests.