1.

A slit of width is illuminated by white light. For red light `(lambda=6500Å)`, the first minima is obtained at `theta=30^@`. Then the value of will beA. `3250Å`B. `6.5 xx 10^(-4)cm`C. `1.3` micronD. `2.6 xx 10^(-4)cm`

Answer» Correct Answer - C
`sin theta = (n lambda)/(a)`, for `n =1, sin theta = (lambda)/(a)`
`:. a = (lambda)/(sin theta) = (6500 xx 10^(-10))/(sin 30^(@))`
`a = 13000 xx 10^(-10)m`
`a = 1.3 xx 10^(-6)m`
`a = 1.3` micron


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