Question

6 Part B Question 1 (20 marks). A source of waves of wavelength A and amplitude a is placed a distance d from a perfectly reflecting surface. The reflected waves can be considered as being due to a source a distance d below the surface, T out of phase with respect to the and oscillating waves from the original source. memor (4 narks) the total wave ow th disturbance at a far distant point P in a direction 8 with respect to the surface can be written 4Td sin 8 (4 marks) Show that the resultant time averaged intensity I at P can be written Lo2a3 7-7o sin 6) and find an expression for /e (4 marks) Illustrate on a polar diagram the dependence of intensity (G)-41.8 on the direction 8 for 0<0 <T/2 if d 31a/4. (Note: and) ()= 19.47 sin sin 048 d 3 4 d (4 marks) What are possible values of d for there to be perfect constructive interference at the direction 0=30. HELP (4 marks) Another source is placed at the same e) height above the mirror but at a distance b to the right of the original source. Deduce relations between d and b and the wavelength A so that one achieves complete constructive interference between all real and virtual sources along the direction 0 30 miror

Answer 1

d) For Perfect constructive interference Intensity is maximum.

From part b)
mar
when
4md sin(30) (2n 1) S (2n1)mT sin 2 (2n1)A 11 11
where n = {0,1,2,3,4....}

PS: I request you to please mention the parts you need us to answer in the question clearly so that we don't miss anything.