WAEC Physics 2018 Paper

Concept:When an object is placed between two plane mirrors inclined at an angle $\theta$, the number of images formed is given by $\frac{360^\circ}{\theta} - 1$.Explanation:Let the angle of inclination between the two mirrors be $\theta$.The number of images formed is $N = \frac{360^\circ}{\theta} - 1$.It is given that $N = 11$.So, $11 = \frac{360^\circ}{\theta} - 1$.Add $1$ to both sides: $12 = \frac{360^\circ}{\theta}$.Now solve for $\theta$: $\theta = \frac{360^\circ}{12} = 30^\circ$.Thus, the mirrors are inclined at an angle of $30^\circ$.Answer:Angle of inclination = $30^\circ$ (Option A).