Suppose that a luminous sphere of radius R1 (such as the Sun) is surrounded by a uniform

Question:

Suppose that a luminous sphere of radius R1 (such as the Sun) is surrounded by a uniform atmosphere of radius R2 and index of refraction n. When the sphere is viewed from a location far away in vacuum, what is its apparent radius? You will need to distinguish between the two cases
(a) R2 > nR1 and
(b) R2 < nR1.