1. WAVES INTERVENTION
A wave is a means of transferring energy from one point to another without there being any transfer of matter between the two points.

2. TRANSVERSE WAVE
Motion of particles perpendicular to motion of wave/energy propagation (wave moving left to right, particles moving up and down)
E.g. wave on a string, electromagnetic waves

3. LONGITUDINAL WAVES
Motion of particles in the same direction as the motion of wave/energy propagation (wave moving left to right, particles left to right)
E.g. sound

4. ANATOMY OF A WAVE Period: time taken for one whole cycle (seconds)
Frequency: number of cycles per second passing a given point (Hz or s-1)

5. Phase difference, θ: amount one wave lags behind the other
Can be measured as an angle (degrees or radians) or as fractions of a cycle

6. If two waves are ‘in phase’ they are both at the same point in the wave cycle

7. THE WAVE EQUATION
For an electromagnetic wave in a vacuum, v = c

8. Overlapping transverse waves usually have their particles vibrating with random orientations so that the resulting vibration direction of the group is continually changing. This is said to be an "unpolarised" wave.
When transverse waves have their particles always vibrating in the same plane, the wave is said to be "plane polarised“ or just “polarized”
Longitudinal waves can't be polarised because their particles vibrate in the same direction that the wave travels.
POLARISATION

9. POLARISATION If

11. Polarisation

12. Polarisation by Reflection (off non-metallic surfaces)
Metallic surfaces reflect light with a variety of vibrational directions; such reflected light is unpolarised.
Nonmetallic surfaces reflect light such that there is a large concentration of vibrations in a plane parallel to the reflecting surface.
If the extent of polarization is large  GLARE

13. APPLICATIONS OF POLARISATION
Polarised sunglasses
3D Movies (two cameras filming with perpendicular polarisation axes)
Television and Radio signals

15. ELECTROMAGNETIC WAVES
EM Waves are transverse waves
Higher frequency = higher ENERGY
All EM waves travel at the same speed in a vacuum (the speed of light!)

16. PRINCIPLE OF SUPERPOSITION
When two waves meet, the total displacement at a point is equal to the sum of the individual displacements at that point

17. STATIONARY WAVES
Superposition of 2 progressive waves with the same frequency moving in opposite directions
Created at specific frequencies of vibration known as harmonics
Do not transmit energy

18. STATIONARY WAVE FORMATION
Blue wave is moving right, green wave is moving left
Resultant wave (from interference of the two waves) shown in black
Nodes are the result of destructive interference
Antinodes are the result of constructive interference

19. HARMONICS First Harmonic (Fundamental Frequency)
Fundamental frequency depends on length, mass and tension of the string/rope
Second Harmonic
f2= 2 f1
Third Harmonic
f3= 3 f1

21. Stationary Sound Waves – important for musical instruments
Stationary Sound Waves – important for musical instruments! Nodes and Antinodes are zones of quiet and loud

22. Stationary Microwaves