Problem

In a Fraunhofer's diffraction by a slit, if slit width is

a

, wave length

\lambda

, focal length of lens is

f

, linear width of central maxima is: (a)

\frac{f\lambda}{a}

(b)

\frac{fa}{\lambda}

(c)

\frac{2f\lambda}{a}

(d)

\frac{f\lambda}{2a}