Wave propagation is any of the ways in which waves pass through a vacuum or medium.
- In physics, propagation refers to the way that light travels in a particular direction or spreads out over time.
- The direction of oscillation and the direction of propagation of light are always at right angles to one another because electromagnetic radiation always takes the form of transverse waves.
- Transverse waves oscillate (vibrate) from side to side and at a right angle to the direction of propagation.