A ray incident on a plane mirror is reflected in a direction such that the angle between the incident and the reflected ray is 90 degree. What are the angles of incidence and reflection? [3Marks]

From the law of reflection, we know that angle of incidence is equal to angle of reflection.

Here, the angle form between the incident and reflected ray= 90 degree {Given}

Let the angle of incidence be y and angle of reflection be also y {as angle of incidence = angle of reflection}

$y+y={90}^{\circ }$ [1 Mark]

or, $2y={90}^{\circ }$

or, $y={\frac{90}{2}}^{\circ }$

or $y={45}^{\circ }$ [2 Marks]

So angle of incidence and angle of reflection are both 45 degrees each