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Consider the arrangement shown in the figure. The distance D is large compared to the separation d between the slits. (a) Find the minimum value of d so that there is a dark fringe at O. (b) Suppose

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प्रश्न

Consider the arrangement shown in the figure. The distance D is large compared to the separation d between the slits. 

  1. Find the minimum value of d so that there is a dark fringe at O.
  2. Suppose d has this value. Find the distance x at which the next bright fringe is formed. 
  3. Find the fringe-width.
संख्यात्मक
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उत्तर

From the figure,

Δx = AMO − ANO

Here AM = MO = √[D2 + d2] AND AN = NO = D

=> Δx = 2(AM − AN) = 2 {√[D2 + d2] - D}

For minima at O,

2 {√[D2 + d2] − D} = (n +(1/2)) λ

Solving above equation for d, we get

d = √[Dλ/2]

(b) width of the dark fringe = w = Dλ/d

Now, the location x is given by

x = Dλ/[2√(Dλ/2)]

=> x = d

(c) As x = w/2

=> w = 2x = 2d

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अध्याय 17: Light Waves - Exercise [पृष्ठ ३८२]

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एचसी वर्मा Concepts of Physics Volume 1 and 2 [English]
अध्याय 17 Light Waves
Exercise | Q 26 | पृष्ठ ३८२

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