By Huygen's wave theory of light, we cannot explain the phenomenon of:

If L is the coherence length and c the velocity of light, the coherent time is 

(1) cL

(2) $\frac{L}{c}$

(3) $\frac{c}{L}$

(4) $\frac{1}{Lc}$

Wavefront is:

1.  locus of all adjacent points at which the phase of vibration of a physical quantity associated with the wave in the same

2.  locus of all adjacent points at which the electric field is the same

3.  series of points on the wave with the same amplitude

4.  series of points on the wave with the same frequency

Huygens' wave theory allows us to know the:

Huygen's principle for secondary wavelets may be used to: