Previous Year Question
The mirror used by the dentists to see the teeth of the patients is:
Convex
Concave
Plane
None of the above
Correct Answer: B
Detailed Solution
A dentist needs to observe a small portion of a tooth as an enlarged and upright image in order to examine cavities, cracks or other abnormalities.
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.
When a tooth is held close to such a mirror, this condition is obtained. The dentist therefore sees an enlarged image, making small details easier to examine.
A Convex Mirror always forms a virtual, erect but diminished image, so it is not suitable for magnification. A Plane Mirror forms an image of the same size.