Problem

Find the thickness of a plate which will produce a change in optical path equal to half the wavelength

\lambda

of the light passing through it normally. The refractive index of the plate is

\mu

. (a)

\frac{\lambda}{4(\mu - 1)}

(b)

\frac{2\lambda}{\mu - 1}

(c)

\frac{\lambda}{\mu - 1}

(d)

\frac{\lambda}{2(\mu - 1)}