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Question : 16
Total: 26
(a) If one of two identical slits producing interference in Young's experiment is covered with glass, so that the light intensity passing through it is reduced to 50 %
(b) What kind of fringes do you expect to observe if white light is used instead of monochromatic light?
(b) What kind of fringes do you expect to observe if white light is used instead of monochromatic light?
Solution:
(a) Finding the (modified) ratio of the maximum and minimum intensities
(b) Fringes obtained with white light
(a) After the introduction of the glass sheet (say, on the second slit),
we have
= 50 % =
∴
=
= √
=
Hence
= (
) 2
= (
) 2 = (
) 2
( ≈ 34 )
(b) The central fringe remains white.
No clear fringe pattern is seen after a few (coloured) fringes on either side of the central fringe.
[Note : For part (a) of this question, The student may
(i) Just draw the diagram for the Young's double slit experiment.
Or
(ii) Just state that the introduction of the glass sheet would introduce an additional phase difference and the position of the central fringe would shift.
(b) Fringes obtained with white light
(a) After the introduction of the glass sheet (say, on the second slit),
we have
Hence
(b) The central fringe remains white.
No clear fringe pattern is seen after a few (coloured) fringes on either side of the central fringe.
[Note : For part (a) of this question, The student may
(i) Just draw the diagram for the Young's double slit experiment.
Or
(ii) Just state that the introduction of the glass sheet would introduce an additional phase difference and the position of the central fringe would shift.
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