To reduce the loss of light when reflected from the glass surface, the latter is covered with a thin layer of a substance, the refractive index of which is n '= sqrt (n), where n is the refractive index of the glass. At what minimum thickness d (min) of this layer will the reflectivity of glass in the normal direction be minimal for light with a wavelength λ?

To reduce the loss of light when reflected from the glass surface, the latter is covered with a thin layer of a substance, the refractive index of which is n '= sqrt (n), where n is the refractive index of the glass. At what minimum thickness d (min) of this layer will the reflectivity of glass in the normal direction be minimal for light with a wavelength λ?