How a Mirror Works

By: Sarah H 2012

What is a Mirror?

A mirror is made out of a thin sheet of glass with a metallic backing, it is often aluminum and is rarely made out of silver, because silver tarnishes and becomes black more easily. Mirrors have greatly evolved over time, a long time ago they were just polished metal discs that very few people could afford. Most poor people used ponds to check their reflection and had to wait in line to do it. It took a long time for the idea of glass to be used as a mirror, probably because glass is see through. You look at a mirror with your eyes so it's very important that we can see things, everything reflects light that's how we can see it.

What is A Plane Mirror?

Plane Mirror Diagram SNH.jpg
Figure one explains how light hits and reflects off a plane mirror.

A plane mirror is a flat mirror, there are three important things to know about plane mirrors, they have an incidence ray, a normal and a reflected ray. When light hits a plane mirror, it is called the incidence ray, the ray of light that is reflected off the mirroris called the reflected ray; and the normal is an invisible line that is at right angles to the mirror. The angle between the normal and the incidence ray is called the angle of incidence. The angle between the normal and the reflected ray is called the angle of reflection. With plane mirrors the angle of reflection is the same as the angle of incidence. All plane mirrors form images of the objects that are reflected in them. It’s important to know that the normal, the incident ray, and the reflected ray are all on the same plane; this is most likely the way that plane mirrors got their name.

What Are Curved Mirrors?

There are two types of curved mirrors, concave, and convex, look at the next paragraph to find out about convex mirrors and look at the paragraph after that to find out about concave mirrors.

Curved Mirror Diagram SNH.jpg
Figure two is of what convex and concave mirrors look like.
What Is A Convex Mirror?

A convex mirror is a mirror that curves outward like an upside down bowl. It can be used as a side mirror on a car, because it lets you see more around you. All convex mirrors form images right side up, unlike concave mirrors. Convex mirrors show images right side up although the image is smaller than it is in real life.

What Is A Concave Mirror?

A concave mirror is curved outward like a bubble. A concave mirror has four different stages of reflection; the first one is if you’re farther from the mirror than the center of the mirror, than you’re reflected upside down and you’re much smaller than you are in real life. The second stage is if you’re at the mirror’s center; you’re the same size as you normally are but you’re still upside down. The third stage is if you’re past the mirrors center although not at the focus of the mirror. The last stage is when you’re at the focus than you’re magnified and right side up. Concave mirrors are used for lots of things, if they’re in a parabola than they can be used to focus powerful beams of light like spotlights, headlamps, flashlight lenses and reflectors. Most people have seen a concave mirrors because all make-up mirrors are concave mirrors.
Mirror Art 1.jpg
Figure three is a circle of mirrors that reflects a beautiful park scene.

What Are Other Curved Mirrors?

Really, the only other type of curved mirror is the ones they use at amusement parks, they don’t have a scientific name, although they’re a mix of concave and convex mirrors. As you’ve probably experienced, these mirror create wacky images of what’s reflected in them. Their are also concave and convex lenses they're like mirrors only they're curved lenses. All mirrors have cool and interesting science behind them, if you want to learn more about them, check out these websites, databases and/or books.


Citations:

Basics of Physics: Exploring Light and Color Colgren Communications, 2004. Full Video.Discovery Education. Web. 13 September 2012.
Flinn, Gallagher. "How Mirrors Work." How Stuff Works. Discovery Education, 2012. Web. 27 Sep 2012.

Gregersen, Erik. "Reflection." The Britannica guide to sound and light. 1st. New York: Britannica Educational Publications, 2011. Print.

Lowe, Lindsey. Introducing Physics Light and Sound. Tucson, AZ. Brown Bear Books Limited. 2010. PRINT.

Glossary:

Angle Of Incidence: the angle between the incident ray and the normal

Angle Of Reflection: the angle at which the incident ray of light leaves the mirror
Focus: an invisible point behind a curved mirror that makes the image clearer

Incident Ray: the ray of light that hits the mirror

Normal: a right angle to a mirror

Parabola: An array of mirrors

Ray Of Light: A light source that started at a point and will always keep on going