In figure, ABC is the cross section of a right-angled prism and ACDE is the cross section of a gless slab. The value of `theta` so that light incident normally on the face AB does not cross the face AC is (given `sin^(-1)(3//5)=37^(@)).`

Options

A. `thetale37^(@)`
B. `thetalt37^(@)`
C. `thetale53^(@)`
D. `thetalt53^(@)`

Answer

b.

Explanation

`A=90^(@)-theta`
`rArr r_(2)=A=90^(@)-theta gt theta_(c)`
`costheta gt sintheta_(c)=(6//5)/(2//3)=(4)/(5)`
`(theta_(C)` is critical angle)
`theta lt cos^(-1)(4)/(5)=37^(@)`