1. WAVES AS 2.3: Demonstrate an understanding of wave phenomenon.

2. Wave Motion Waves move energy and information around without moving mass. Waves move energy and information around without moving mass. Waves can be mechanical or electromagnetic. Waves can be mechanical or electromagnetic. Waves can be transverse or longitudinal. Waves can be transverse or longitudinal. Waves can be moving or stationary. Waves can be moving or stationary.

3. Mechanical Waves Mechanical waves consist of vibrating particles called the medium. The speed of a mechanical wave depends on the medium. E.g. Sound waves travel faster in water than in air. Mechanical waves consist of vibrating particles called the medium. The speed of a mechanical wave depends on the medium. E.g. Sound waves travel faster in water than in air. Examples of mechanical waves include: Examples of mechanical waves include: Sound waves, water waves.

4. Electromagnetic Waves Electromagnetic waves require no medium at all. These waves consist of vibrating energy fields. Electromagnetic waves require no medium at all. These waves consist of vibrating energy fields. They all travel at the same speed: the speed of light, c = 3x10 8 ms -1 They all travel at the same speed: the speed of light, c = 3x10 8 ms -1 Examples include: Examples include:

5. Transverse Waves The particles oscillate (move back and forth) perpendicular to the direction of the wave. E.g. water waves. The particles oscillate (move back and forth) perpendicular to the direction of the wave. E.g. water waves.

6. Longitudinal Waves The particles oscillate in the direction that the wave is travelling. E.g. sound waves. The particles oscillate in the direction that the wave is travelling. E.g. sound waves. Demonstration The air particles oscillate side to side – the same direction the wave is traveling.

7. The Slinky Experiment

8. Waves Terminology Frequency applet E.g. f = 50Hz What is T? Frequency (f) = number of waves each second. E.g. 3 Hz means 3 waves per second. The units for frequency are Hertz (Hz). T is the period, the time for one wave. (s)

9. Waves Terminology Amplitude (A) is the size of the wave: Amplitude (A) is the size of the wave: The wavelength is the distance from crest to crest or from trough to trough: The wavelength is the distance from crest to crest or from trough to trough: λ Applet λ Applet λ Applet

10. The wave equation The velocity of a wave is given by the formula: The velocity of a wave is given by the formula: V = velocity (ms -1 ) f = frequency (Hz) = wavelength (m) Example: Shaking the slinky 3 times per second. The waves are measured to be 0.8m. Find: (a) The period of the wave. (b) The speed of the wave. Wave equation applet

11. Water Waves Waves are reflected off barriers, obeying the same laws of reflection as light. Waves are reflected off barriers, obeying the same laws of reflection as light.