How do mirrors work?

In order to understand how mirrors work we have to understand light. Light consists of waves and light wave itself is invisible to us. But light waves have information that our brain can interpret. What we actually see is an image constructed by our brain using the light waves bouncing off various objects.

In the case of mirror, the mirror reflects the light waves that are bouncing off the object back in the direction of the object. Human eyes perceive this reflection as if there was an object behind the mirror and light waves are bouncing off that.

_{Image attribution - Zaereth/ CC BY-SA 4.0}

In more scientific terms the working of mirrors can be explained using the laws of reflection. The law of reflection states that the light ways bounces off the mirror following certain rules. The incoming angle of incidence is always equal to the angle leaving the surface, also known as the angle of reflection.

This principle is easily understood in a plane mirror as it has a flat surface.

However it can be more confusing when applied to a curved mirror. Assume a light wave travelling in front of the mirror in a straight line. When you place a plane mirror in the path of the light, it hits it with an angle of incidence 0. Based on the laws of reflection this light would be reflected back at an angle of 0. Now if you move the light source to different part of the mirror it will still reflect back in a straight line as the mirror is flat and the angle of incidence is always the same. But let’s say you put a curved mirror in the path of the light source. If you move the light source to different parts of the mirror you will notice that the light is not reflected in a straight line any more. This is because the angle of incidence will vary due to the curvature of the mirror. Depending on the type of curved mirror the images will sometimes appear to have been distorted, enlarged, smaller and sometimes inverted.