Determine the thickness of a plate required to produce a change in the optical path equal to half the wavelength of light travelling through it normally. The plate has a refractive index of .

Step-by-step solution

Let the thickness of the plate be t . The optical path of light travelling through the plate of thickness t and refractive index is t . The optical path of light travelling through the same distance t in vacuum is t . The change in the optical path introduced by the plate is x = t - t = ( - 1)t . Given that the change in the optical path is equal to half the wavelength , we have: ( - 1)t = 2 t = 2( - 1)