The correct answer is (b). A dentist mirror is a concave mirror. Concave mirrors are curved inward at the center, like the inside of a bowl. They reflect light in such a way that the light rays converge at a point in front of the mirror. This makes objects appear larger than they actually are. Dentists use concave mirrors to examine hard-to-reach areas of the mouth, such as the back teeth.
A cylindrical mirror is a mirror with a cylindrical surface. The mirror reflects light in such a way that the light rays are parallel to each other after reflection. This makes objects appear the same size as they actually are. Cylindrical mirrors are used in some telescopes and microscopes.
A convex mirror is a mirror with a convex surface. The mirror reflects light in such a way that the light rays diverge after reflection. This makes objects appear smaller than they actually are. Convex mirrors are used in some security mirrors and rearview mirrors.
A plane mirror is a flat mirror. The mirror reflects light in such a way that the light rays are reflected back in the same direction that they came from. This makes objects appear the same size as they actually are. Plane mirrors are used in many everyday objects, such as mirrors in bathrooms and bedrooms.