A person is looking at the flat surface of a transparent hemispher of refractive index `mu-sqrt(2)` . Half of the flat surface is coloured black and half of curved surface is coloured in six equally spaced strips as shown in Figure. Then

Options

A. the person can see green, orange and red
B. the person can see only yellow, indigo and blue
C. the ray coming from red and organge strips will be totally reflected
D. the ray coming from yellow, indigo and blue stips will be totally reflected

Answer

b.,c.

Explanation

Let C be the critical angle: ` sinC=(1)/(mu)=(1)/(sqrt(2))`
`C=45^(@)`
For Y,I and B, angle of incidence at a point on QP can be less than C, so they will be refracted from QP and can be seen by person
But for G,R and O, angle of incidence at a point on QP will be more than C. Hence, they will be internally reflected.