1. Announcements 9/30/11 Prayer About that exam… a. a.Review session this afternoon, 4 pm, room C460 b. b.In Testing Center, Saturday morning until Thursday evening c. c.No textbook, no notes d. d.I will give you a list of equations (but not all equations!), and all constants/conversion factors/materials parameters you need e. e.Can use your own calculator, but you’re on your honor not to store extra stuff in calc. memory f. f.No time limit, but “time goal” is 2 hours avg (took me 33 mins)

2. What to study? I’d recommend in this order: a. a.Homework b. b.Class notes c. c.Old exams d. d.Book More on the exam xkcd Some more specifics about the exam… Chris office hours today: 3-4 pm

3. Waves Skipping: Oscillations, Ch. 15 a. a.If you don’t recall “simple harmonic motion”, please review on your own. Starting next lecture: Some sections from Physics Phor Phynatics, Dr. Durfee’s book Starting lecture after that: Complex numbers a. a.Clicker: Have you seen: e ix = cosx + isinx ? A = “have seen” B = “not” C = “maybe, but I can’t remember”

4. Reading quiz Which of the following phenomena do NOT exhibit a combination of transverse and longitudinal waves? a. a.sound waves in air b. b.surface water waves c. c.waves in the earth generated by an earthquake

5. Wave intro: some math What do these functions look like? a. a.f(x) = x 2 b. b.f(x) = (x – 1) 2 Think: What would be an equation for a parabola that moves 1 m to the right every second? What will this function look like at 0 s? at 1 s? at 2 s? a. a.f(x) = (2x – 6t) 2 b. b.What is its “velocity”?

6. Sinusoidal waves Nothing special about parabolas… What does f(x) = cos(x – vt) look like at t = 0? at t = a little later? Add in “amplitude” Add in “phase” How to change spatial period? What if you want wave to move right-to-left instead of left-to-right? “Wave function”

7. Wave properties Definition: oscillating disturbance that transfers energy (but not mass). Direction of travel Direction of oscillation: transverse vs longitudinal Medium Examples… a. a.Water b. b.Earthquake (P & S) c. c.Sound d. d.Light e. e.Rubber tubing (demo) f. f.Slinky (demo) Wikipedia: “S-wave”

8. Did you say “Slinky”? The handing out of the slinkies a. a.We have about 35 b. b.There are 34 students registered for the class

9. Web demo http://paws.kettering.edu/~drussell/Demos/waves/wavemotion.html

10. Wave properties, cont. Web demo: Stokes’ “Traveling Sine Wave” http://stokes.byu.edu/sinewave_script_flash.html Wavelength a. a.meters/wave Period T a. a.seconds/wave Frequency ( f = 1/T ) a. a.waves/second Speed v a. a.m/s v = f

11. Wavefunction Let’s call it “s(x)” for now (because “f” is used for frequency) What are the units of s? What does s really represent? a. a.For transverse waves… b. b.For longitudinal waves… What does s(x) represent?

12. The (Linear 1D) Wave Equation Why is it called the wave equation? a. a.Because traveling waves are solutions of the equation! Any function that has “x-vt” will work! …or “x+vt” What’s that funny symbol? C = v 2

13. k and  What’s the difference between these: General form of cosine wave: …sometimes written as: k = “wavevector”;  = “angular frequency”  = _______