Consider an optical medium where refractive index varies linearly with height i.e. n(y)=n(0)+k y where k is a positive constant and y is the height above the ground level. Here positive number n(0) is the refractive index at the ground level. The refractive index at height y varies with temperature at that point as (n(y)- 1) T(y)= constant. Consider a ray propagating (in a plane) in the medium which is horizontal at