Question

A dentist’s mirror is placed 3.4 cm from a tooth. The enlarged image is located 6.5 cm behind the mirror. (a) What kind of mirror (plane, concave, or convex) is being used? (b) Determine the focal length of the mirror. (c) What is the magnification? (d) How is the image oriented relative to the object?

Answer 1

As the image is enlarged, it means the mirror is a concave mirror and focal length is positive for a concave mirror

using mirror equation

1/f = 1/di + 1/do

where di is image distance and do is object distance and f is focal length

as image is behind the mirror, di = - 6.5 cm

so,

1/f = 1/3.4 - 1/6.5

f = 7.129 cm

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magnification

m = - di / do

m = - ( - 6.5) / 3.4

m = 1.911

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as m is positive, image is upright.