question_answer

What is the effect on the interference pattern observed in a Young's double slit experiment in the following cases: (i) Screen is moved away from the plane of the slits. (ii) Separation between the slits is increased. (ii) Widths of the slits are doubled.                

Answer:

                Fringe width, \[\beta =\frac{D\lambda }{d}\] (i) As\[\beta \propto D,\], so when screen is moved away from the slits, fringe width increases. (ii) As\[\beta \propto 1/d,\] so when the separation between he slits is increased, fringe width decreases. (iii) When widths of slits are doubled, contrast between maxima and minima decreases due to the overlapping of interference patterns formed by various narrow pairs of the two slits.