The magic of a mirror: how is it able to show your reflection? Premium

Discover the science behind mirrors and glass, from electron behavior to topological materials, explained by IIT Kanpur professor.

Dressing up is probably one of the most annoying things. You stand in front of a mirror and try to find the right combination of clothes of various colours hoping you look more tolerable to people. This is probably one trait that distinguishes us from other animals: we spend a few good minutes every morning staring at a mirror.

Have you ever wondered, though, when we stare at a mirror, what we’re really staring at?

Most mirrors feel like glass. They are heavy and break easily. But then if you stare at a glass, say your window, and you stare at a mirror, what you see are very different things.

On a bright day, glasses are transparent, and you can see the outside world through a glass window. At night, if you look at your window and if you are in a well-lit room, you will now see yourself. In a mirror, on the other hand, you always see yourself irrespective of whether it is day or night (and as long as it is not dark).

To understand the difference between a mirror and window glass, we need to learn about metals and insulators.

Metals are shiny things, like your steel cups and plates, the aluminium pressure cooker, and coins in your purse. Metallic objects are usually hard, not easy to break, and have a silvery shine. They also get hot and cold quite easily and can conduct current. It’s one reason why we never touch a live socket using a spoon. Insulator objects on the other hand are made of glass, wood, and plastics. The things that usually don’t conduct current also often don’t look silvery.

An electric current is conducted by electrons. Atoms have both positively charged protons and negatively charged electrons. In a metal, electrons are like unruly, fun-loving kids: they leave their parent atoms and move around between different atoms, forming a big soup of electrons. On the other hand, in an insulator, every electron in an atom is a bit shy and stays close to the parent atom. Therefore when we put in a battery and try to push the electrons, they will move freely in a metal, since they are unruly, but in an insulator they won’t. Therefore metals conduct current, insulators don’t.