1.

A glass wedge of angle 0.01 radian is illuminated by monochromatic light of wavelength 6000 Å falling normally on it. At what distance from the wedge will 10th dark fringe be observed by reflected light ? (mu = 1.5) :

Answer»

`0.1 MM`
`0.2 mm`
`0.3 mm`
`0.4 mm`

Solution :Here `theta = 0.01` radian
`lambda = 6000 Å = 6000 xx 10^(-10) m`
`x_(n) = ? , n = 10`
Now `t = x_(n) theta= x_(n) xx 0.01`...(i)
`mu = 1.5`
Condition for maxima is `2 mu t = n lambda`
`t = (n lambda)/(2MU) = (10 xx 6000 xx 10^(-10))/(2 xx 15) = 2 mu m`...(ii)
From EQN.(i),
`x_(n) = (t)/(theta) = (2)/(0.01) = 200 mu m = 0.2 mm`
`THEREFORE x_(n) = 0.2 mm`.


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