Please Explain The Huygens Principle?????

Huygens principle can be stated as follows: 1.Every point on a wavefront is a source of secondary disturbance that propagates as light waves. 2.The secondary disturbance propagates in all directions with speed of light. 3.The secondary disturbance spreads out as hypothetical spheres, each one of them may be called wavelet. 4.The tangential surface to the secondary wavelets is called secondary wavefront. 5.The intensity (I) of secondary disturbance varies as- I is directly proportional to (1+cos a) where `a` is angle between direction of propagation of secondary disturbance and original direction of propagation of light. See diagram for Huygens Principle in your textbook.

Oops! You are a college student. I thought you are in 12th grade.