Comparison of Images Formed By Plane, Cylindrical (Concave Side), and 
Spherical (Concave Side) Mirrors
 
Ellen Springer  Nazareth Academy 
Robert Tisdale  Julian H. S.
Levi Johnson    Otis Elementary
Alex Economou   C. V. S.       

Objectives:

1) To distinguish between horizontal and vertical axes and to 
   recognize that ones eyes lie along a horizontal axis and ones 
   forehead and chin lie along a vertical axis.
2) To describe plane, cylindrical, and concave mirrors in terms of 
   curvature about horizontal and vertical axes.
3) To help students discover that image reversal occurs when the axis 
   of the object is parallel to the axis of curvature of the mirror, 
   and that no reversal occurs when the axis of the object is parallel 
   to a linear mirror axis. 

This exercise can be done: 
1) Anytime during the year as an attention grabber and an exercise in 
   observation and interpretation.
2) As an introduction to mirror images.
3) As a review of mirror images.

Apparatus needed:

Plane mirror, cylindrical mirror, short focal length concave mirror.

Notes: The cylindrical mirrors can be made by gluing a 10 cm by 10 cm 
piece of aluminized mylar inside of a 120o section of carpet roll 
tubing. In order to avoid confusion which is associated with left and 
right when observing mirror images, it seems best to describe 
orientation along the horizontal axis in terms of some objects in the 
room, such as window side and door side. 

Recommended strategy:

1) Beginning with the plane mirror ask the student to cover one eye 
   with their hand and observe the image of their face. Describe the 
   image as reversed or not reversed top to bottom, or window side to 
   door side. Turn the mirror through 90o and observe the image again. 
2) Using the concave side of a cylindrical mirror repeat procedure 
   no.1 asking the same questions. 
3) Using the concave side of a spherical mirror repeat procedure 
   no.1 asking the same questions.
4) Summarize student observations on the board and help the class 
  explain their observations.
5) Observations in a cylindrical mirror can be extended by viewing 
   the image of two different colored arrows crossed at 90o. Ask the 
   students to turn the object through 90o and observe what happens to 
   the image. Then ask the students to turn the mirror through 90o and 
   observe what happens.