PH-UY 1013 Lecture Notes - Lecture 7: Total Internal Reflection, Medium Mark B, Electromagnetic Radiation
Document Summary
Displacements are vectors, their direction matters: similar to functions. Waves can be plotted with x and y coordinates. When x (position) is the same, add y (height) Displacements in the same direction are added, constructive interference. Displacements in opposite directions are subtracted, destructive interference. Waves of equal amplitude, frequency, wavelength, and speed, moving in opposite directions. Some locations will always have constructive interference, some will always have destructive. Always destructive: nodes (a. 2. a. 1) fixed ends are always nodes (a. 2. a. 2) nodes always have zero displacement. Always constructive: antinodes (a. 2. b. 1) free ends are always antinodes (a. 2. b. 2) antinodes oscillate between zero and maximum displacement: resonance. Objects have natural frequencies at which the oscillate (esp. springs, swings, pendula, wine glasses) If force is applied at the same frequency, displacement will increase every cycle. Without energy losses (damping), displacement will increase indefinitely. Doppler effect: waves from a moving source. Since the medium (air) isn"t moving, wave speed is constant.
