Plane mirrors
Beginner
Form virtual images as far behind as the object is in front.
A plane mirror gives a virtual, upright, same-size image as far behind the mirror as the object is in front, with left–right reversal. A person needs only a half-height mirror to see the whole body.
Rotating a mirror by θ turns the reflected ray by 2θ.
The image can't be projected on a screen.
In more detail
A plane mirror forms a virtual image that is the same size as the object and as far behind the mirror as the object is in front. The image is laterally inverted.
Real-world uses
- Bathroom mirrors and periscopes use plane mirrors.
- Dressing rooms use multiple plane mirrors to show different views.
- You see your face in a bathroom mirror at the same distance behind the glass as you stand in front of it.
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Frequently asked questions
Why does a mirror reverse left and right?
It reverses the direction perpendicular to the mirror, so left and right appear swapped.
Is the image real?
No, it is virtual, because light only appears to come from behind the mirror.
Why is the image virtual?
Light appears to come from behind the mirror, but no light actually passes through that point, so the image cannot be projected onto a screen.
Related topics in Optics
Nature of light · Rectilinear propagation · Reflection of light · Spherical mirrors · Mirror equation · Magnification of a mirror