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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, (iii) width of the slits are doubled. Give reason for your answer. |
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Answer» SOLUTION :(i) As fringe width `BETA=(lamdaD)/(d)`, hence `betapropD`. Thus, as the screen is moved away from the plane of the slits, the fringe width increases. (II) As fringe width `betaprop(1)/(d)`. Thus, as the separation between the slits is increased, the fringe width decreases. (iii) Each slit of the double-slit produces its own diffraction effect. ANGULAR width of central diffraction band due to each slit `theta=(lamda)/(a)` where a=width of each slit) should be much more that the angular width of interference band `alpha=(lamda)/(d)`. it is so because waves from two slits will interfere only when they DIFFRACT widely so as to superimpose on one another. hence, for good visibility and formation of good quality interference fringes `(lamda)/(a) gt gt (lamda)/(d)` and it leads to the combination of narrow slits and each narrow slit forms its own intererence pattern. due to their overlapping resultant pattern becomes blurred. |
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