Previous Year Question
The mirror used by a dentist to examine the teeth of patients is:
A.
Concave
B.
Convex
C.
Plane
D.
Cylindrical
Correct Answer: A
Detailed Solution
A dentist needs to observe a small portion of a tooth as an enlarged and upright image for close examination. When an object is placed between the Pole and Focus of a concave mirror, i.e. at a distance smaller than its focal length, the image formed is virtual, erect and magnified.
Placing the tooth close to a concave mirror produces this condition. The enlarged image makes it easier to observe cavities, cracks and other small details.
A convex mirror always produces a diminished and erect virtual image, so it is not suitable for magnifying a tooth. A plane mirror produces an image of the same size.