Question: A dentist uses a curved mirror to view teeth on the upper side of the

Question

Question: A dentist uses a curved mirror to view teeth on the upper side of the mouth. Suppose she wants an erect image with a magnification of 2.00 when the mirror is 1.25 cm from a tooth. (Treat this problem as though the object and image lie along a straight line.)

Part A) What kind of mirror (concave or convex) is needed? Use a ray diagram to decide, without performing any calculations.

Part B) What must be the focal length and radius of curvature of this mirror?

Part C) Draw a principle-ray diagram to check your answer in part (b)

My thoughts: s = 1.25 cm, and s'/s = 2.00 are given fromt he problem,

from this you can find that s' = 2.50 cm

To my knowledge, convex mirrors only produce images that are DIMINISHED, upright, and virtual. Thus, the image cannot be created by a convex mirror since although the image would be erect, the magnification would not be 2, which would create a LARGER image.

Concave mirrors, on the other hand, DO produce ERECT, AND LARGER images, but only when the object is to the right of the focal length, which if you calculate is not the case.

1/f = 1/s + 1/s'

1/f = 1/1.25 + 1/2.50

f = 0.83 cm

R = 2f

R = 2(0.83 cm)

R = 1.67 cm

This puts the object in between R and f, NOT to the right of f, and thus creates an INVERTED although larger image, which is not what we want.

After all this speculation, I am utterly confused and need help. Please look over this and tell me what I'm doing wrong!

Explanation / Answer

a) concave

b) 1/f = 1/1.25 + 1/

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