Submerged Light, Refraction Snells law maybe?

[bmb2009]

Homework Statement

A green light is submerged 2.70 m beneath the surface of a liquid with an index of refraction 1.39. What is the radius of the circle from which light escapes from the liquid into the air above the surface?

Homework Equations

Honestly I didn't even know where to start with this one... any guidance on what to do ?

Thanks!

The Attempt at a Solution

 

[haruspex]

You correctly mention Snell's law in the title. Do you understand how it leads to total internal reflection?

 

[bmb2009]

Just did some more research and i figured it out.. thank you!