1.

The slit width, when a light of wavelenght 6500Å is incident on a slit, if first minima for red light is at `30^(@)` isA. `1xx10^(-6) cm`B. `5.2xx10^(-6) cm`C. `1.3xx10^(-6) cm`D. `2.6xx10^(-6) cm`

Answer» Correct Answer - C
`lamda=6500A^(@),n=1,a=?theta=30^(@)`
For `n^(th)` mininma, `sintheta=nlamda`
`:.a=(nlamda)/(sintheta)`
`=(1xx6.5xx10^(-7))/(sin30)`
`1.3xx10^(-6)m`


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