What is the maximum radius that this circle could have?

[gamesandmore]

A point source of light is submerged 2.6 m below the surface of a lake and emits rays in all directions. On the surface of the lake, directly above the source, the area illuminated is a circle. What is the maximum radius that this circle could have?

No idea where to begin this one - nair = 1.00 nwater = 1.33 and
n1sin01 = n2sin02

 

[Doc Al]

Draw yourself a picture showing various rays of light emitted in all directions. What happens as they hit the surface of the water? Examine how the angle of incidence relates to the angle of refraction.