Two plane mirror are inclined to eachother at an angle `theta = 70^(@)`, Fig. A ray `SO` of light falls at some angle `i` on the mirror `M_(1)`, falls after reflection from it, on the other mirror `M_(2)` from which it gets reflected along a direction parallel to the plane mirror `M_(1)`. Find the value of `/_i`.

Answer

`40^@`

Explanation

As ray reflected from `M_2` is parallel to `M_1`, Fig.
`:. /_2 = theta = 70^@ (Cosses. /_s)`
Also, `/_1 = /_2 = 70^@`
In `Delta OAC, theta + /_ 1 + /_AOC = 180^@`
`70^@ + 70^@ + /_AOC = 180^@`
`/_AOC = 180^@ - 140^@ = 40^@`
According to the laws of reflection,
`/_i= /_AOC = 40^@`.