1. Vocabulary Review Properties of Waves The Electromagnetic Spectrum

2. Vocabulary Review Progressive waves Describing wave motion
Displacement
Amplitude
Wavelength
Period
Frequency
Speed

3. Intensity Energy passing through a unit area in unit time.
Intensity ~ Square of the amplitude
I ~ A2
Intensity ~ 1/d2
Where d is distance from source

4. Example 1
A health inspector is measuring the intensity of a sound. Near a loudspeaker his meter records an intensity I. This corresponds to an amplitude A of the sound wave. At another position the meter gives an intensity reading of 2 I. What is the corresponding sound wave amplitude?

5. Example 2
The intensity I of a sound at a point P is inversely proportional to the square of the distance x of P from the source of the sound. Air molecules at P, a distance r from S, oscillate with amplitude 8.0 μm. Point Q is situated a distance 2r from S. What is the amplitude of oscillation of air molecules at Q?

6. Phase
The angle at which the wave motion started.

7. Phase 0⁰
180⁰ or п

8. Phase
90⁰ or п/2
270⁰ or 3п/2

9. Phase Difference
The difference in angles between two waves at a specific point.

10. Phase Difference
Phase difference of п at all points

11. Phase Difference
Phase difference of п at all points

12. Coherence
When two waves have constant phase difference, then they are coherent.
Coherence occurs when two waves have the same frequency or period.

13. Non-Coherence

14. In Phase
Phase difference is a multiple of 2п at all points.

15. Out of Phase
Phase difference is not a multiple of 2п.

16. Out of Phase
Phase difference of п at all points

17. Wave Properties For all waves Reflection Refraction Diffraction
Bouncing of waves off a surface
Refraction
Change of wave speed as it passes from one medium to another (from one depth to another)
Bending of waves
Diffraction
Bending of waves around a barrier

18. Wave Properties Question
Which wave properties change when light passes from air into glass?
A colour and speed
B frequency and wavelength
C speed and wavelength
D wavelength and colour

19. Polarisation Oscillation that takes place in one direction.
Only true for transverse waves.

20. Polarisation

21. The Electromagnetic Spectrum
Electromagnetic waves are transverse waves
They are non-mechanical waves
Do not require a medium to transfer energy
Travel at the same speed in a vacuum
3 x 10 8 ms-1

22. Orders of Magnitude (Wavelength)
Gamma Rays
X-Rays
Ultraviolet Rays
Visible Light
ROY G BIV m
10-10 m
10-7 m
10-7m
(700 nm -400 nm)

23. Orders of Magnitude (Wavelength)
Infrared
Microwaves
Radio Waves
10 -6 m
10-2 m
10 2 m