1.

Visiblelight of wavelength 6000 xx 10^(-8) cm fall normally on a single slit and produces diffraction pattern. It is found that the second diffraction minima is at 60^(@) from the centre maxima. If the first minima is produced at theta is close to

Answer»

`20^(@)`
`25^(@)`
`30^(@)`
`45^(@)`

Solution :For second minimum,
`d sin theta= 2lambda`
`:.sin theta=(2lambda)/(d)`
`:. Sin 60^(@)=(2lambda)/(d)`
`:. (sqrt(3))/(2)=(3lambda)/(d)`
`:. (lambda)/(d)=(sqrt(3))/(4) ""...(1)`
For first minimum,
`d sin theta = lambda`
`:. sin theta=(lambda)/(d)`
From EQUATION (1),
`:. sin theta=(sqrt(3))/(4)`
`:. sin theta=0.4330`
From table of sine,
`theta=25.65(@)`
`:. theta~~25^(@)` (NEARER value)


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