The mirror used by the dentists to see the teeth of the patients is

The correct answer is B) concave. A dentist's mirror is a small concave mirror. The dentist holds it close to the tooth, inside the focal length, so the mirror forms a magnified, erect, virtual image. That enlarged upright view is what lets the dentist inspect small surfaces clearly.

• A) Convex: Wrong. A convex mirror always gives a diminished, erect image. That suits rear-view mirrors because it gives a wide field of view, not close inspection.
• C) Plane: Wrong. A plane mirror gives an image of the same size, with no magnification.
• D) None of the above: Wrong, because B is correct.

The core concept is the position of the object relative to the focus of a spherical mirror. Placing an object between the pole and the focus of a concave mirror gives magnification. The same principle is used in shaving and make-up mirrors. For Mains, it links to applications of optics in medicine, such as the ophthalmoscope and dental and surgical instruments.

Trap: Aspirants often pick convex because the dentist's mirror looks small and curved. Remember that the image quality, not the size of the mirror, decides the type.