1. EM Waves, Superposition
Oscillations & Waves
EM Waves, Superposition

2. Electromagnetic Waves
A special type of transverse wave
Do not require a medium
Generated by the motion of charged particles
Propagated as variations in EM field
Speed in free space, c = 3 x 108 m s-1

3. Electromagnetic Waves

4. The Electromagnetic Spectrum

6. The Visible Spectrum
The visible portion of the spectrum is the equivalent of a single frame in a reel of film. . .
km long!

7. Interacting Pulses
What happens when two pulses travelling in opposite directions meet?

8. Interacting Pulses
What happens when two pulses travelling in opposite directions meet?

9. Interacting Pulses
What happens when two pulses travelling in opposite directions meet?

10. Interacting Pulses
What happens when two pulses travelling in opposite directions meet?

11. Interacting Pulses
What happens when two pulses travelling in opposite directions meet?

12. The Principle of Superposition
The displacement at any point is the algebraic sum of the displacements due to each pulse and/or wave.

13. Interference
Wave superposition can be constructive . . .

14. Interference
. . . or destructive

15. Path Difference
Observe two identical waves sources separated by a distance

16. Path Difference (d2 - d1) = nλ constructive interference
(d2 - d1) = (n + 1/2)λ destructive interference
NB: n is an integer S1 S2 d1 d2
Observer

17. Phase Difference
Interference can also be characterized by synchronization, or phase difference

18. Resultant of Two or More Waves
Complex waveforms may be represented as the superposition of many simple waveforms

19. Examples

20. DTMF – Dual Tone Multi Frequency
Phone systems listen for and recognize combinations of pure sine waves
These combinations are very unlikely to be produced in human speech

22. Beat Frequency
Superimposing waves of similar frequency yields a beat pattern

23. Summary EM Waves and the EM Spectrum The Principle of Superposition
Interference
Constructive and destructive
Path and phase difference
Resultant of two or more waves
Examples of wave superposition

24. Homework In Tsokos: Ch 4.1 - #3, 6, 8, 9, 12, 15, 17, 25, 29, 31, 37