# State the main characteristics of wave normal & Wave front.

##### Characteristics of wave normal

I. It gives the direction of propagation of wave.

II. It is perpendicular to wave front.

III. In a homogeneous isotropic medium, wave normal is same as direction of ray of light.

IV. It is drawn from the point of generation of wave front.

##### Characteristics of wave front:

i. Wave fronts travel with the speed of light in all directions in an isotropic medium.

ii. The phase difference between any two points in the same phase on the two consecutive wave fronts is 2π. So, if the phase at a crest is 2π, then phase at next consecutive crest = 4π and so on. Hence at any crest, the phase is 2nπ and phase at any trough is  (2n + 1) π, where n is an integer.

iii. It always travels in the forward direction. During the propagation of spherical wave front from a source, wave becomes weaker. It is so because same energy is distributed over circumference of larger circles of increasing radii.

iv. In anisotropic medium, it travels with different velocities in different directions due to variation in densities of the medium.