Ray Optics and Optical Instruments Part 1

From the given figure, We know that,
µ=‌

1

sin‌iC

Here, ic is the critical angle of incidence and µ is the refractive index.
µ=‌

1

sin‌45∘

⇒µ=1.414
The rays will emerge out when angle of incidence is less than the angle of critical angle of glass-air interface PR.
As µR<µ while µC and µB>µ, so only red colour will be transmitted through face PR while green and blue rays will suffer total internal reflection.