A beam consisting of red, blue and yellow colours is incident normally on the face AB of an isosceles right-angled prism ABC as shown in the figure given below. Critical angle of glass-air interface for yellow colour is 45°.

Out of the four emergent rays P, Q, R and S, which one is for the yellow colour :

1. P
2. Q
3. R
4. S

Q

Reason — As the critical angle for yellow colour is 45°, so it suffers refraction along the line AC of the prism.