μ1=1.68,μ2=1.44μ1/μ2=1/sini1⇒i1=59o
For critical angle, total internal reflection takes place when i>i1
maximum angle of reflection is 90−i1=31o=rmax
Let imax be the maximum angle of incidence.
μ1=sinimax/sinrmax⇒imax=60o
Thus all the ray between 0o<i<60o will suffer TIR.