Dispersion/total internal reflection

[cerberus9]

Homework Statement

Consider a common mirage formed by superheated air just above a roadway. A truck driver whose eyes are 2.00 m above the road, where n=1.0003 looks forward. She has the illusion of seeing a patch of water ahead on the road, where her line of sight makes an angle of 1.20 degrees below the horizontal. Find the index of refraction of the air just above the road surface. (Hint: Treat this as a problem one involving total internal reflection)

Homework Equations

\Theta_c=sin^-1(n₁/n₂)

n₁sin\Theta₁=n₂sin\Theta₂

The Attempt at a Solution

So since the textbook said to treat it as a problem with total internal reflection, i figured that I would solve for \Theta_c and so I did

\Theta_c=sin^-1(n₁/n₂)
\Theta_c=sin^-1(1/1.0003)
\Theta_c= 88.6

and I just have absolutely no idea what to do from here.

 

[rl.bhat]

n1*sin(theta 1) = n2*sin(theta 2)
In the problem n1, theta 1 and theta 2 is known. Find n2.