1. Place a piece of cardboard on the
table in front of you. Place a piece of white paper over the
cardboard. Stand a mirror, long edge down, at the center of the
paper. Hold in place with a block of wood. Draw a line behind
the mirror to show where the mirror is located in case it is
moved accidentally.
2. In front of the mirror draw a triangle
(blue lines) and label corners of the triangle ABC. Place
an observation pin at point X at left and Y at right. Place a
pin at A on the triangle.
3. {It is important
that you get your face at the level of the tabletop when looking
into the mirror.}
Looking over the top of pin X, look
into the mirror at the image
of pin A. Carefully place pin R (as
close as possible) at the mirror so that pins X, R, and the image
of A line up. Remove mirror. Draw lines AR & RX.. Extend
RX behind the mirror as a dashed line.
Light is traveling along path AR &
RX to reach your eye. Because your brain knows that light travels
in straight lines, your eye is fooled into believing that light
is coming from a pin located along the red dashed line. But where
on the dashed line? Remove pin R.
4. Repeat steps 2 & 3, this time
from the right-hand observation point Y. Now draw AR' & R'Y.
Extend as a dotted line R'Y until it intersects with the extension
of XR. The point of intersection represents the perceived location
of the virtual image of pin A.
5.Repeat stps 2-4 for pins located at
the other vertices of the blue triangle.
6. How well did you do?
a) Draw a line from Object Point A to Image Point A'. The line
drawn in step 1 to represent the reflecing surface should be
perpendicular to this connecting line and should bisect it. ditto
B-B' and C-C'.
b) Fold the paper on the line representing the reflecting surface
(from step 1). The blue
triangle ABC should be congruent to
the image triangle A'B'C' and should cover it.