Question

In a YDSE with two identical slits, when the upper slit is covered with a thin, perfectly tranparent sheet of mica, the intensity at the centre of screen reduces ro `75%` of the initial value. The second minima is observed to above this point and third maxima below it. which of the following can not be a possible value of phase difference caused by the mica sheet
A. `(pi)/(3)`
B. `(13pi)/(3)`
C. `(17pi)/(3)`
D. `(11pi)/(3)`

Answer 1

Correct Answer - A
Phase diff.at `O`
`I_(R)=2I(1+cosphi) rArr (3)/(4)xx4I=2I(1+cosphi)`
`1+cosphi=(3)/(2) rArr cosphi=(1)/(2)`
`phi=(pi)/(3),(4pi)/(3)`
Path diffence=`(mu-1)t`
For given condition
`(3lambda)/(2)lt` path diff. `lt3lambda rArr 3pilt`phase diff`lt6pi.`