Optics 6 Question 47
49. A vessel of width has two small slits and sealed with identical glass plates of equal thickness. The distance between the slits is . is the line perpendicular to the plane and passing through , the middle point of and . A monochromatic light source is kept at below and from the vessel, to illuminate the slits as shown in the figure alongside. Calculate the position of the central bright fringe on the other wall with respect to the line . Now, a liquid is poured into the vessel and filled upto . The central bright fringe is found to be at . Calculate the refractive index of the liquid.
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Answer:
Correct Answer: 49.
Solution:
- Given
Path difference between
Now, let at point
Path difference between
Central bright fringe will be observed when net path difference is zero.
Therefore, central bright fringe is observed at
Alternate solution
or
or
or
or
or
(b) The central bright fringe will be observed at point