A beam of light consisting of red, green and blue colours is incident on a right-angled prism. The refractive indices of the material of the prism for the red, green and blue wavelengths are 1.39, 1.44 and 1.47 respectively. The prism will

The colour for which $i>{\theta }_c$  , will get total internal reflection:
 

$i>0_c$   or  $\sin i>\sin {\theta }_c$
or  $\sin {45}^0>\frac{1}{\mu }or\frac{1}{\sqrt{2}}>\frac{1}{\mu }$
or for which $\mu >\sqrt{2}$ or  $\mu >1.414$
Hence, the rays for which $\mu >1.414$ will get TIR.
For green and blue $\mu >1.414$  , so they will suffer TIR on face AC, only red comes out from this face.