## Lecture 10: Phasors and Standing Waves

February 20, 2018

• Study: Ex 14.6; Supp. Fig. 1.4
• Ignore: Eq 14.13 (it's not wrong -- just too specialized to be useful)

### Objectives

• (Continuing objective) Describe applications of the concepts of induction, waves, and light to everyday real life'' situations.
• Given a specific expression for a traveling transverse or longitudinal harmonic wave in sinusoidal or complex exponential form, determine amplitude, angular frequency, frequency, wavenumber, wavelength, period, phase shift and wavespeed.
• Correctly sketch phasor diagrams to represent an oscillating system at various times.
• Calculate the beat period and frequency for two signals differing slightly in frequency.
• For standing wave modes on strings or in air columns in pipes: sketch the wave pattern, identify nodes and antinodes, and determine wavelength, wave-number, frequency or wave speed. Write down the complex exponential expression for a given standing wave.

### Homework

• Wednesday's Assigned Problems: A32, A33, A34, A92, A112, X3 (CLICK HERE); CH 14: 38, 39; Supp CH 1: 1, 2

Answers: CH 14 #38 (a) 4 m, (b) 14 Hz

• Monday's Hand-In Problems: A35, A37, A88, A104; CH 14: 40, 68; CH 32: 34; Supp CH 1: 3, 4, 6