Question

A dentist uses a spherical mirror to produce an upright image of patients tooth which is magnified by a factor of 4.5 when placed 1.8 cm from the tooth a) what type of mirror is used (b) what is the focal length of the mirror

Answer 1

The mirror used is concave mirror and the focal length is 0.52 cm

Explanation:

Given data:

• Magnification factor = 4.5
• Distance of image = 1.8 cm

(a) The mirror used by the dentist is concave mirror .

(b) According to mirror lens formula  

M = v / u

4.5 = 1.8 / u

u = 1.8 / 4.5 = 0.4 cm

1 / f = 1 / v + 1 / u  

Mirror formula:

1 / f = 1 / 1.8 + 1 / 0.4

1/f = 10 / 18 + 10 / 4

1/f = 20 - 90 / 36

1 / f = - 70 / 36

1 / f = - 1.94

f = 1  / 1.94

f = - 0.52 cm

Thus the mirror used is concave mirror and the focal length of the mirror is 0.52 cm