A glass prism `(mu = 1.5)` is dipped in water `(mu = 4//3)` as shown in figure. A light ray is incident normally on the surface AB . It reaches the surface BC after totally reflected, if

Options

A. sin`theta ge 8//9`
B. `2//3 lt sin theta lt 8//9`
C. `sin theta le 2//3`
D. it is not possible

Answer

A

Explanation

For TIR at face AC
`theta ge i_(c ) `

`rArr " " sin theta ge sin i_(c )`
`rArr " " sin theta ge (1)/(n_(gw))`
`rArr " " sin theta ge (n_(w))/(n_(g)) rArr sin theta ge (8)/(9)` .