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Do you want to stimulate some critical thinking in your classroom? Tell your
class that we do not see living or inanimate things; we only see the light
reflected from those things. This is a perfect introduction to the topic of
mirrors. After discussing the validity of the statement, ask your students
what they would see if the classroom were totally dark. Remind them that no
thing can be seen unless it is luminous (emitting light) or being
illuminated (reflecting light). A mirror reflects light, producing a clear
image of the object that is in front of it. Then why are not all objects
mirrors? Because not all surfaces reflect light in parallel straight lines.
Rough surfaces can reflect a lot of light, but no image. This is because the
reflected rays travel in random straight lines. A smooth surface reflects
light in parallel straight lines that produce a clear image of an object.
Clear, still water was one of the earliest mirrors. The Egyptians invented hand mirrors of polished metal around 1500 BC. Today, flat mirrors are made from plate glass with a thin reflective layer of aluminum or silver sprayed or condensed on the back. Mirrors come in many shapes and sizes. In Part 1, I discuss the optical characteristics of plane (flat) mirrors. This discussion is followed by a simple demonstration and a lab activity with an extension. In Part 2, to be published next month, I will discuss concave and convex mirrors with a simple demonstration and a brief lab activity following each discussion. These activities are designed for students in middle school through college. Plane mirrors A real image is formed by light reflected from an object. A virtual image is formed by light reflected from the surface of a mirror. A virtual image itself never reflects any light, but for the observer it seems to be formed behind the mirror as the reflected light of the object returns from the mirror’s surface. The virtual image in a plane mirror is an upright, left-to-right reversal of the object’s real image and always appears to be behind the mirror’s surface. Demonstration: Images in plane mirrors Students can prove that all images from a plane mirror are virtual ones. Ask a student to hold up his or her right hand in front of a plane mirror. The result is similar to the “mirror image” our hands make when they are placed together palm to palm. Have the student then move his or her hand toward the mirror and then away from it. The virtual image remains the same size as the student’s hand and appears to be at the same distance behind the mirror as the student’s hand is in front of the mirror. The virtual image in a plane mirror is an upright, left-to-right reversal of the reflected object’s real image. This can be demonstrated by having the student write the word “bib” on a piece of paper and then holding it up to the mirror. The word “bib” becomes “did” in the mirror. Not only is the order of the letters reversed, but also the orientation. Emergency vehicles sometimes have their names written upright and reversed on their hoods. Why? Lab activity 1: Locating the virtual image behind a plane mirror. Materials
Note: Refer to the photo below as needed when placing the pins. 
Materials
Take your students' curiosity to the next level with these great Carolina kits and products.
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