20.a)state Huygen's principals.b)Using it,construct the reflected wavefront as plane incident wavefront strikes the surface.c)Use this diagram to show that i =4

20.a)state Huygen's principals.b)Using it,construct the reflected wave

1.	20.a)state Huygen's principals.b)Using it,construct the reflected wavefront as plane incident wavefront strikes the surface.c)Use this diagram to show that i =4
Answer» <p>Huygens Principle states that(a) Each point on a wavefront becomes a source of secondary disturbance which spreads out in the medium.(b) The position of wavelength at any later instant may be obtained by drawing a forward common envelop to all these secondary wavelets at that instant.(c) In an isotropic medium, theenergycarried by waves is transmitted equally in all directions.(d) If the initial shape, position, the direction of motion and the speed of the wavefront is known, its position at a later instant can be ascertained by geometrical construction. Note that the wavefront does not travel in the backward direction.</p>