Why do mirrors reflect light

Most of us use mirrors every day without stopping to reflect on how they actually work. Considering the near-magical function mirrors perform, their construction is surprisingly simple.

Most household mirrors are made of glass with a thin layer of metal backing usually aluminum , and several layers of paint. Instead, the glass surface of a mirror performs a predominantly protective function, preserving the extremely thin, extremely smooth layer of metal behind it. Light passes through the glass part of the mirror and is reflected by the metal.

Light is an electromagnetic field, and when it hits a mirror the metal inside of it usually aluminum or silver cancels out the electric field parallel to the mirror which causes it to change directions and reflect away. Not all reflective mirrors are conductive though - a certain percentage of light will reflect wherever there is a change between two types of materials like air and water, because the electric field changes as it goes though different materials some of the light will get reflected while the rest will pass though or be absorbed.

Thanks for the great question! Mirrors reflect light because of how "difficult" it is for light to travel through the material that the mirror is made of. A very common mirror materials is highly-polished silver. To understand why mirrors reflect, first think about light in outer space where there is no atmosphere.

In outer space light can travel without being reflected, scattered, or impacted by any surrounding atoms or molecules like mirror atoms or gas molecules. Once light enters the Earth's atmosphere, some of the light begins to be impacted by the gas molecules in the Earth's atmosphere, but this impact is very small so the light can still keep traveling forward very "easily".

So if one illuminates a metal with a source of single photons, there will be complete reflection and no heating of the metal in most cases and complete absorption with associated heating creation of so-called phonons in the metal in some cases. Follow David Biello on Twitter. Already a subscriber? Sign in. Thanks for reading Scientific American. Create your free account or Sign in to continue. See Subscription Options. Go Paperless with Digital.

David Biello is a contributing editor at Scientific American. Get smart. Sign up for our email newsletter. Sign Up. Lifelong habit. My cooking is all done on electric, only "high" or "off. I suppose the mirrors make use of "residual light. I just live "differently," and what i assume is "smarter.

BIG huge help is flipping the breaker off and on for the hot-water heater if it's electric. Immediately afterward, flip it off. You'll have hot water enough for a day and possibly half the electric bill by following these principals. Emma Peel, El Paso Texas USA Light is a tricky thing, a light placed against a mirror will reflect almost all of the light however the light itself will be in the way causing a bit of a shadow, wasting more of the light.

As you get farther from the light source the amount of light drops exponentially, so mirrors 10 feet from a bulb may only receive 10 percent of the usable light energy so the reflection at this point will be a little less than 10 percent of the original power. Then this 10 percent reflected drops exponentially again. They absorb some, significantly less. While the light cannot go on forever, it can certainly be spread further with well placed mirrors.

The fact that the light is being reflected rather than absorbed means it is there longer. While it is technically the same wave, it is longer, therefore it is having more light in the room. You are not doubling, or adding light, you are just losing less light than what you were if you had say a black wall. Mikey A. Depending on the perspective of an individual viewer it will appear as if one can view such distance as one would physically.

In these areas of the surface are what allow light to absorb and and reflect emitting a wider range of light, herein giving the semblance of "more" light. Zyan Kol, Pumbaya Malta I just observed a very bright bathroom.

No lightbulbs were lit. The morning Sun was shining in the window and the rays were hitting the vanity mirror, then hitting a smaller mirror on the opposite wall next to the window.