2. Everyday examples of waves

A wave can be described as a regular disturbance that transfers energy.

This uniform pattern of movement allows the wave to transfer energy in various forms at a particular frequency.

To transfer this energy the particles vibrate or the bulk material oscillates in some way, but the particles or material stay in the same place - only the energy 'moves'!

This description is fine for example ..

1. When you drop a stone in a pond you see ripples on the surface of the water as the kinetic energy of the impact is transferred in all directions as water waves. If the ripple meets a floating object, that object just bobs up and down as the ripples pass by - the object is not carried along. This is an example of a transverse wave, the vibrations/oscillations at 90^o to the direction of wave movement - more details later.

Waves crashing on the seashore or battering a pier, is a good examples of waves transferring energy!

2. When you play a musical instrument the sound of the notes, that is the energy of the vibration (string or reed etc.), is transferred to your ear by the particles of air vibrating-oscillating to and fro in line with the direction of the sound wave is travelling - this is an example of a longitudinal wave - more details later. The air does NOT move along in the direction of the waves, only the sound energy is transferred.

3. However these descriptions of waves don't completely fit electromagnetic radiation e.g. radio, microwave, infrared, visible light, uv, X and gamma rays. In this case the energy is carried by photons, which have wave properties, but they do actually move from one place to another e.g. from the Sun to Earth or reflected light by which you see objects. BUT, they still transfer energy e.g. infrared radiation transfers thermal energy from the Sun to the Earth's surface, visible light energy triggers a response on a photographic plate or a photosensitive electronic photocell.

The first two examples, 1. and 2. above, require a medium e.g. air or water, but electromagnetic radiation can travel through a vacuum as well as transparent materials like air, water or glass.

However, the vibrations-oscillations of the photons due to their wavelike properties occur at 90^o to the direction of travel, so they are transverse waves.