1.

A lens has focal length f. It gives diffraction pattern of Fraunhoffer type of a slit giving width of w. If the wavelenth of light used is lambda, then what is the distance of first dark band and next bright band from axis?

Answer»

`(a)/(lambda)F`
`a lambda f`
`(lambda)/(a)f`
`(lambda)/(af)`

Solution :`OMEGA SIN theta = n lambda`
n = 1
`sin theta = (lambda)/(omega)`
`Rightarrow theta = (lambda)/(omega)`
If distance of FIRST dark fringe is x, then `theta = (x)/(f)`.
So, `(x)/(f) = (lambda)/(a), x = (lambda)/(a)f`.


Discussion

No Comment Found

Related InterviewSolutions