- The phenomenon of propagation of light how occurs is explained by Huygens’ principle.
- The locus of all the points to which all the wave reaches at a time or simultaneously so that all that points are in the same state or phase. Such locus of points is called as wave front.
- And the normal or perpendicular drawn at any point on the wave front which is in the direction of propagation of light is called as wave normal.
- The following figure shows the wave front and wave normal.
- There are two types of wave fronts are possible namely spherical wave front and the plane wave front also.
Principles:
1.) Every point on the wave front produced acts as the secondary source of light and that secondary source of light emits secondary waves in all possible directions.
2.) These new wave fronts produced which are secondary wave fronts are found to be more effective in forward direction only that means in the direction of propagation only.
3.) If we draw a tangent to all the secondary wave fronts at that point then it gives the resultant wave front at any position.