Question

why r newtons ring circular in shape n how they r produced????

Answer 1

Newton's rings are producedwhen the light is reflected between two surfaces - a sphericalsurface and an adjacent flat surface. In the resultant interference pattern, areas of same brightness are determined by the difference of phases of waves, thickness of the medium material traversed (e.g. air). These are points that are equidistant from the point of contact of the two surfaces, i.e.circles.