Question

Figure shows a mixture of blue, green and red coloured rays incident normally on a right angled prism. The critical angles of the material of the prism for red, green and blue are $46^\circ$, $44^\circ$ and $43^\circ$ respectively. The arrangement will separate

• A. red colour from blue and green
• B. blue colour from red and green
• C. green colour from red and blue
• D. all the three colours.

Answer 1

Answer: (A)

red colour from blue and green

Answer 2

Condition of no emergence is
$A>C$
As angle of prism is greater than critical angle for blue and green coloured rays, total internal reflection will take place at second surface and hence the arrangement will separate red colour from blue and green.