With the aid of a simple diagram: (i) illustrate how interference is observed with llyod's mirror apparatus. describe expressions to locate the minima and maxima in the interference pattern.
with the aid of a suitable diagram (ii) explain how a thin film of refractive index n can be used as an anti-reflective coating on a glass lens with refractive index ng.

One kind of e-book display consists of millions of very small spheres that float in a thin fluid layer between two conducting transparent plates. each sphere is black on one side and white on the other, and possesses an electric dipole moment directed from the white side to the black. when an electric field is applied between the plates, the spheres rotate so that their dipole moment lines up with the field. depending on the fields direction, either the black or the white sides of th espheres can be made visible.the dipole moment of the spheres can be modeled as two opposite charges of magnitude 3.5 x 10^-15 c, separated by a distancce of 100 micrometers (um). what is the maximum possible torque on a sphere if the electric field between the transparent plates is 4.0 x 10^5 n/c