You are using a mirror and a camera to make a self portrait....

You are using a mirror and a camera to make a self portrait. You focus the camera on yourself through the mirror. The mirror is a distance $\mathrm{D}$ away from you. To what distance should you set the range of focus on the camera? a) $D$ b) $2 \mathrm{D}$ c) $\mathrm{D} / 2$ d) $4 \mathrm{D}$

You are using a mirror and a camera to make a self portrait. You focus the camera on yourself through the mirror. The mirror is a distance $\mathrm{D}$ away from you. To what distance should you set the range of focus on the camera?
a) $D$
b) $2 \mathrm{D}$
c) $\mathrm{D} / 2$
d) $4 \mathrm{D}$

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Key Concepts

Plane Mirror Image Formation

This concept explains that a plane mirror produces a virtual image that appears to be located behind the mirror at a distance equal to the distance from the mirror to the object. In problems like this, although the object is D away from the mirror, the light path behaves as if the object were located 2D away (D to the mirror and D from the mirror to the image), which is key to determining the effective distance to focus upon.

Camera Focusing and Effective Distance

This principle involves understanding that a camera lens must be focused at the distance where the subject (or its image) appears to be. When using a mirror, the effective subject is the virtual image formed behind the mirror. Therefore, the camera should be focused at twice the actual object-to-mirror distance, which in this case is 2D. This understanding of effective distance is crucial in setting the correct focus for clear imaging.

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