lecture32 - Beats; Interference Text sections 18.7; 18.1...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
Text sections 18.7; 18.1 Text sections 18.7; 18.1 Beats; Interference Practice: Chapter 18, problems 9, 51, 67 Beats Beats Two waves of different frequencies arriving together produce a fluctuation in power or amplitude. Since the frequencies are different, the two vibrations drift in and out of phase with each other, causing the total amplitude to vary with time. y time 1 beat
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
time t in phase 180 o out of phase in phase Same amplitudes, different frequencies: ) cos( 1 0 1 t A y ω = ) cos( 2 0 2 t A y = Trigonometry: cos a + cos b = 2 cos [(a-b)/2] cos [(a+b)/2] Result: + = + = t t A y y y 2 cos 2 cos 2 2 1 2 1 0 2 1 slowly-varying amplitude SHM at average frequency The math:
Background image of page 2
Note maximum power when “amplitude” part is 2A 2 beats per cycle of t 2 cos 2 1 ω # beats/second = × 2 2 2 1 f f The beat frequency (number of beats per second) is equal to the difference between the frequencies:
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 6

lecture32 - Beats; Interference Text sections 18.7; 18.1...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online