$(a)$ Why does a ray of light passing through the centre of curvature of a concave mirror after reflection get reflected back along the same path?
$(b)$ Why are convex mirrors commonly used as rear-view mirrors in vehicles?
$(c)$ $A$ pencil partly immersed in water in a glass tumbler appears to be displaced at the interface of air and water. Name the phenomenon of light responsible for it.

(N/A) ray of light passing through the centre of curvature of a concave mirror strikes the mirror surface at an angle of $90^{\circ}$ (normal incidence). According to the laws of reflection,when a ray falls normally on a surface,it reflects back along the same path.
$(b)$ Convex mirrors are used as rear-view mirrors because they always form an erect,virtual,and diminished image of objects. This provides a wider field of view,allowing the driver to see a much larger area behind the vehicle.
$(c)$ The phenomenon responsible for the apparent displacement of the pencil is the refraction of light.