Properties of light:

The wavefronts can be of different shapes depending on the size and shape of light source and the distance from it. Huygens' principle states that every point on a wavefront behaves as the source of small secondary wavelets which spread out in all directions with a velocity equal to the velocity of light. The new wavefront is then found by constructing a surface of envelope tangential to the secondary wavelets.

Applying Huygens' principle, the phenomenon of reflection and refraction could be explained. The velocity of water waves depend on the depth of the water. The principle of superposition of waves states that when two or more waves travel through the same portion of a medium simultaneously, the resultant displacement at any point is the vector sum of the displacements due to the individual waves.