1. Waves Waves which move forward are called PROGRESSIVE waves. Waves transfer energy. Waves do not transfer matter. Waves can be classified as either mechanical waves or electromagnetic waves

2. mechanical waves Mechanical waves are disturbances in a medium. All mechanical waves need a medium Examples are waves on water, sound waves in air, waves on stretched strings, waves on slinky springs. The wave in fact is caused by particles becoming displaced about a point. Each particle drags its neighbour with it.

3. Electromagnetic waves Electromagnetic waves can travel through a vacuum and are disturbances in electric and magnetic fields. There progress is impededto some extent by the presence of matter.

4. TRANSVERSE WAVES Although the wave is travelling along the axis the particles which make up the wave are moving ACROSS the direction of travel. The wavelength is the distance between any two equivalent points on the wave. The amplitude of the wave is the maximum displacement of the paticles (for a mechanical wave) above or below the equilibrium position (the wave axis)

5. ` Equivalent points on the wave are said to be in phase ` One wavelength `

6. Longitudinal waves Examples; sound waves,waves on a slinky spring

7. The displacement of each particle is around a single point on the wave axis but along the line of travel One wavelength Notice that the particles are in phase when separated by one wavelength