Activity 3 
When you look in a mirror, your reflection sometimes appears to be behind the mirror's surface.  Light rays reflecting off the mirror create this illusion, often called a virtual image.  In this activity, you explore the relationship between the position of an object and the apparent position of its reflection in a mirror. 
Exploration 1 
a. 	On your sheet of graph paper from the exploration in Activity 2:   Position a tinted plastic reflector along the x-axis with points P and Q on your side of the reflector. 
Mathematics Note 
The reflection of an object is its image.  The object itself is the preimage. If point A is the preimage, then the image of a point A can be represented as A' (read "A prime"). 
b. 	1. 	Find the reflection of point Q in the reflector. 
2.	Place your pencil behind the reflector and mark the point on the graph paper where the reflection of Q appears to be.  This point is the image of Q.  Label it Q'. 
3.	Remove the reflector and draw PQ'.  As shown in Figure 10, points P, C, and Q' should be collinear. 
 
c.	1.	Use the plastic reflector to mark the image of point P on your
graph paper.  Label this point P'.

2.	Remove the reflector and draw QP'.

d. 	The distance from a point to a line is the distance along a path perpendicular to the line.  Measure the distance from the x-axis to each of the following points: 

1.	x-axis to Q		_____mm
2.	x-axis to Q'		_____mm
3.	x-axis to P		_____mm
4.	x-axis to P'		_____mm
 
e. 	Make a conjecture about the relationship between the distance from an object to the mirror line and the distance from its image to the mirror line.