Physics

Problem

Dentists use small spherical mirrors to view enlarged, upright images of teeth that are only a few centimetres from the mirror surface. Suppose such a mirror has a focal length of

2.0\,\text{cm}

. (a) Determine the range of object distances (expressed in relation to the focal length) for which this mirror will produce an upright, enlarged image. (b) A tooth is positioned

1.5\,\text{cm}

from the mirror. Calculate the image distance and the magnification. State whether the image is real or virtual and comment on its size relative to the tooth. (c) The tooth is then moved to

5.0\,\text{cm}

from the mirror. Repeat the calculations in part (b) and discuss how this change affects the dentist’s ability to see fine detail. (d) Explain qualitatively why a convex mirror would not be suitable for the purpose described, even though it can also produce upright images.

Intuitive explanation

This is about concave mirrors and magnification—the key insight is that when you place an object between the mirror's focal point and the mirror surface itself, the mirror acts like a magnifying glass, producing an enlarged, upright virtual image. You'll need to use the mirror equation and magnification formula to find where the image forms and how much larger it appears than the actual tooth.

Intuitive explanation

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