Two plane mirrors are placed at an angle `theta`so that a ray parallel to one mirror gets reflected parallel to second mirror after two consecutive reflections .The value of `theta`will be-

Explanation

ray`AB` goes to mirror`M_(1)`gets reflected and travels along `BC` and then gets reflected by `M_(2)` and goes to `CD` Direction .It the angle between `M_(1)` and `M_(2)` be `alpha` ,then
In `DeltaOAB /_OBCand/_OCB` are equal to`alpha`
`:.3alpha=180^(@)`
`alpha=60^(@)`
Hence correct answer is `(2)`