A dentist uses a curved mirror to view teeth on the upper side of the mouth. Sup
ID: 1731613 • Letter: A
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.) (a) What kind of mirror (con- cave or convex) is needed? Use a ray diagram to decide, without performing any calculations. (b) What must be the focal length and radius of curvature of this mirror? (c) Draw a principal-ray diagram to check your answer in part (b), 3.Explanation / Answer
givne magnification = 2
erect image
m = +2
u = -1.25 cm
a. for erect image of above one magnificaiton, the concave mirror is required and the object needs to sit between the focal point and ht epole ofthe mirror
b. focal length = f
1/v + 1/u = 1/f
m = -v/u = 2
v = -2u = 2.5 cm
hence
1/2.5 - 1/1.25 = 1/f
f = -2.5 cm
R = 2*f = 5 cm
c. the answer can be checked easily by plotting the case where the object is betwen the focal length and the pole of the mirror