PHY138 – Waves, Lecture 3 Today’s overview The Wave Model Speed of Waves on a String Sinusoidal Waves Spherical Waves, Plane Waves

Reading Assignment This week’s reading assignment from the text by Knight is: Chapter 20, Sections There is also an article on Medical Ultrasound available on the web-page for Wednesday’s Lecture (Waves Lecture 4). Suggested Chapter 20 Exercises and Problems for Practice: 1, 25, 35, 39, 53, 69, 71, 79, 82 (79 is funny!)

Last time: 14.8 Externally Driven Oscillations Resonance!

Transverse versus Longitudinal

Snapshot Graph

History Graph

A string of beads are connected by a set of tiny springs. At the instant the clock starts (t=0), a pulse is moving to the right on the beads and the snapshot graph looks like this: Which of the following history graphs tracks the position for the bead marked with a red arrow as a function of time?

The graph at the top is the history graph at x = 4 m of a wave traveling to the right at a speed of 2 m/s. Which is the history graph of this wave at x = 0 m? (A) (B) (C)

Sinusoidal Waves

What is the frequency of this traveling wave? A. 10 Hz B. 5 Hz C. 2 Hz D. 0.2 Hz E. 0.1 Hz Quiz 2

What is the phase difference between the maximum of a wave and the adjacent minimum? (crest to trough) A. 0 B. π /4 C. π /2 D. 3 π /2 E. π Quiz 3

Sinusoidal Wave Snapshot Graph k = 2π/λ is the wave number

Sinusoidal Wave History Graph ω =2 π/T is the angular frequency