How does the double-sided mirror in the interrogation rooms work?

By applying theory related to the intensity of light and making mirrors, humans have created two-dimensional mirrors that serve in many fields.

Surely, you've seen two-way mirrors appear in interrogation rooms on movies. These special mirrors allow people from outside to see the interior, to observe suspects, but people from the inside cannot look outside.

So why can these two-dimensional mirrors be able to do so? The answer will be explained in this article.

This special mirror allows people from outside to see the space inside, but people from the inside cannot look outside.

How often do mirrors differ from two-dimensional mirrors?

According to Wonderful Engineering, a conventional mirror undergoes a mirror-coated process, then coated with reflective materials such as silver, tin, nickel or aluminum. The front is a transparent glass plate, a metal oxidation avoidance layer and a reflective coating.

When light enters the glass and touches the metal surface, the light will reflect back. That's why you can see the mirror image of yourself when you look in the mirror.

However, two-dimensional mirrors also use this metal layer but are thinner than conventional mirrors. The coating of reflective molecules covers half of the total surface area of ​​the mirror and the other half gives light to pass through.

Principle of operation of two-sided mirrors.

This feature explains why, you can see that the interrogation room space is always bright with the opposite room conditions to the darkest possible space, avoiding the light transmitted through the interrogation room.

The two-sided mirror we often see on movies.

Two-way mirrors operate on the principle of light intensity . If the light intensity on both glass surfaces is the same, the mirror will look like a normal piece of glass. But when the light is concentrated on one side and the other side is dark, the glass plate becomes a mirror with the person in the light-filled space. This phenomenon is quite obvious when you try to look out the door at night but only see the indoor lights reflecting more.

Tips to distinguish two-dimensional mirrors in practice

There is a trick to distinguish two-way mirrors and conventional mirrors quite easily. Put your finger on the mirror surface. If you see a gap between the tip of your finger and the reflected image inside, it's a normal mirror. But if two fingers touch each other, you may be looking at a two-way mirror and the risk of being monitored.

If two fingers touch, you may be looking at a two-way mirror.

Two-way mirrors have many applications, especially in interrogations, scientific research, security monitoring markets or creating special stage effects.