# Wavetrains and Coherency. © 2006 Walter Fendt Beats Animation

## Presentation on theme: "Wavetrains and Coherency. © 2006 Walter Fendt Beats Animation"— Presentation transcript:

Wavetrains and Coherency

© 2006 Walter Fendt Beats Animation http://www.walter-fendt.de/ph11e/beats.htm

y(x) = Sin x © SPK

y(x) = [Sin x + Sin (1.08 x)]/2 © SPK

y(x) = [Sin x + Sin(1.04 x) + Sin (1.08 x)]/3 © SPK 0 < x < 200

y(x) = [Sin x + Sin(1.02 x) + Sin (1.04 x) + Sin(1.06 x) + Sin (1.08 x)]/5 © SPK 0 < x < 400

y(x) = [Sin x + Sin(1.01 x) + Sin (1.02 x) + Sin(1.03 x) + Sin (1.04 x) + Sin (1.05 x) + Sin (1.06 x) + Sin (1.07 x) + Sin (1.08 x)]/9 © SPK 0 < x < 400

y(x) = [Sin x + Sin(1.01 x) + Sin (1.02 x) + Sin(1.03 x) + Sin (1.04 x) + Sin (1.05 x) + Sin (1.06 x) + Sin (1.07 x) + Sin (1.08 x)]/9 © SPK

Solitary pulse

For -L +L E0E0

Fourier integral

k p =2

Wave packet or Wave group for k p =k

Frequency Bandwidth Range of frequency k (or ) in wavetrain ( k) (or

Temporal coherence: Coherence time: Coherence length: © SPK

Spectral lines from helium gas tube

A characteristic Spectral line

Red Cadmium= 6438 Å = 10 10 Hz, 30 cm Yellow Sodium = 10 9 3 cm = 5893 Å He-Ne Laser 6328 Å 300 m = 10 6 Hz, © SPK

Kr discharge lamp has roughly the following intensity distribution at various wavlengths, (in nm), Estimate the coherence length of the Kr source.

Coherence time Coherence length