Question

Write true or false for the following statements:
When a plane mirror is turned by a angle $\theta$, the reflected rays turns by an angle $\theta .$

• A. True
• B. False

Answer 1

The correct option is B False

The plane mirror when incident with ray of light at an angle, it reflects the ray at the same angle. But when the mirror is rotated by an angle of $\theta$, ray reflected will have twice the angle as 2 $\theta$, because of the following reason,

As we know, Angle of incidence = Angle of reflection

Assume ,

Angle of incidence = Angle of reflection = $\angle$ $\lambda$ - {$i$}

Therefore when plane mirror is rotated by $\theta$ angle, the normal is moved by $\theta$ angle and angle of incidence, so angle of incidence 2 will now becomes –

Angle of incidence =$\angle$ $\lambda$ + $\angle$$\theta$

So, Angle of reflection will now be :-

Angle of reflection =$\angle$$\theta$ + $\angle$ $\lambda$ + $\angle$$\theta$

Angle of reflection = 2$\angle \theta +\lambda$ - {$ii$}

Subtracting equation {$i$} from {$ii$}, we get

The reflected ray turns by 2$\angle \theta$.