Ray diagrams are a method of modeling using principles of reflection to give a reasonable
method of showing the location, size, and type of image that is produced by a mirror. The ray
diagrams DO NOT describe exactly how the light produces an image seen by a person, but allow
us to have a fairly accurate idea of the resulting image.
Rules Governing Mirror Ray Diagrams
•
•
•
The law of reflection is obeyed – Incident rays parallel to the principal axis reflect in line
with the focus
Light is reversible –
o Incident rays in line with the focus will reflect parallel to principal axis.
o Incident rays in line with the center of curvature are reversed back along the
same path.
Light along the principal axis reverses back along the principal axis
Ray diagram procedures
1. Make sure that both c and f are present (at least one will be provided)
2. Drawing Rays: only two of the three rays are necessary
• RAY 1 – Draw an incident ray from the top of the object to the mirror, parallel to
the principal axis.
! REFLECTED RAY LINES UP WITH FOCUS
• RAY 2 – Draw an incident ray from the same point on the object to the mirror,
lined up with c.
! REFLECTED RAY REVERSES PATH
• RAY 3 (optional) – Draw an incident ray from the same point on the object to the
mirror, in line with the focus.
! REFLECTED RAY IS PARALLEL TO THE PRINCIPAL AXIS
3. The top of the image occurs where the reflected rays intersect.
• NOTE: As long as the bottom of the object is on the principal axis, the bottom of
the image is also. (all three rays would be on the axis)
c
f
CONCAVE SPHERICAL MIRROR
CONVEX SPHERICAL MIRROR
c
c
Convex mirrors
c
Concave mirrors
c
c
RAY DIAGRAM WORKSHEET – Part 1
1
2
3
4
NAME________________________
5
6
7
RAY DIAGRAM WORKSHEET – Part 2
NAME________________________
For each mirror, measure and record the object distance, object size, center of curvature, and
focus to the nearest millimeter. Then use the mirror equation to calculate what the image
distance should be and use the magnification equation to calculate what the image size should
be. Remember, anything on the opposite side of the mirror from the object has a negative
magnitude, indicating that light cannot actually be there.
1. c=
f=
p=
h=
2. c=
f=
p=
h=
3. c=
f=
p=
h=
4. c=
f=
p=
h=
5. c=
f=
p=
h=
6. a)
c=
f=
p=
h=
b)
c=
f=
p=
h=
7. a)
c=
f=
p=
h=
b)
c=
f=
p=
h=
CONCAVE MIRRORS
p>c
Attributes:
________________
c
________________
________________
Attributes:
p=c
________________
________________
c
________________
Attributes:
f<p<c
________________
c
p = f (once you find f, put an object at that distance as well)
________________
________________
Attributes:
________________
c
________________
________________
Attributes:
p<f
________________
________________
c
________________