The circular boundary of the concave mirror subtends a cone of half angle `theta` at its centre of curvature. The minimum value of `theta` for which any ray incident on this mirror parallel to the principal axis suffers reflection more than once is
.

Options

A. `30^(@)`
B. `45^(@)`
C. `60^(@)`
D. `75^(@)`

Answer

B

Explanation

`theta=90^(@)-theta`
`theta=45^(@)`