Optics

# Visual field of a plane mirror

The closer an observer is to the mirror, the wider his field of vision.

Virtually everyone has mirrors: in their homes, in the car, some in bags, etc. What we see through a mirror is called an image . Generally speaking, a plane mirror is a well-polished metallic surface capable of reflecting light. Generally, in making a mirror, a glass plate is used where a very thin silver or aluminum chamber is placed on one of its faces.

In a plane mirror, the conjugate image is virtual, upright, the same size as the object and positioned symmetrically to the object with respect to the mirror plane. In short, the image and the object are located at the same distance.

We call the visual field of a plane mirror the entire region that an observer can see by reflection. The visual field is greater the closer the observer is to the mirror. Let’s see the figure below: in it we have an observer O and a plane mirror E .

In order to graphically determine the visual field of this mirror for the observer, we must find the image O’ of this mirror, symmetrical with respect to the mirror, and trace the segments O’A and O’B .

The rays incident at points A and B , the ends of the mirror, which reach the observer by reflection, determine, for him, the visual field of the mirror, which is the shaded region in the figure above. Any object point placed in the visual field of the mirror is seen by reflection by the observer O.