According to Huygens’ Principle, each point on a wavefront is treated as if it is a source of new, smaller wavelets, called secondary waves. These wavelets spread out in all directions from that point at the same speed as the original wave.
This idea means that a wavefront doesn’t just move forward as a solid wall of energy. Instead, it is made up of countless individual points, and each of these points sends out tiny spherical waves. After a short period of time, these spherical waves overlap, and their combined outer edge (or envelope) forms the new wavefront. This new wavefront then becomes the starting point for the next set of secondary wavelets, and the process repeats.
By using this method, Huygens’ Principle explains how waves:
- Move through space in a straight line,
- Bend when entering a new medium (refraction),
- Curve around edges (diffraction),
- Reflect off surfaces.
So, in essence, each point on a wavefront acts like a miniature source, helping to build the next stage of the wave’s journey. This concept is key to understanding the wave behavior of light and other types of waves.