PASCO OS-8500 INTRODUCTORY OPTICS SYSTEM User Manual
Page 36
Introductory Optics System
012-02744K
®
30
Virtual Images
In the previous part of this
experiment, you tested the
Fundamental Lens Equation
only for the concave mirror,
and only for those cases in
which a real image was focused
between the object and the
mirror. However, when an
object is placed between a
concave mirror and its focal
point, a virtual image is formed.
Virtual images can also be
formed using a convex spheri-
cal mirror.
In the Appendix of this manual,
read the section titled “Locating
Virtual Images”. Construct a
table similar to Table 12.1 and
use the Image Locators to
collect your data. Remember, for a virtual image, d
i
is negative.
➀ Are your results compatible with the Fundamental Lens Equation? If not, to what do you attribute the
difference? _________________________________________________.
Repeat the procedure with the convex side of the Spherical Mirror.
➁ Does the Fundamental Lens Equation hold for images formed by convex spherical mir-
rors?______________________________________________________________.
Spherical Aberration
Adjust the position of the Light Source and Crossed Arrow Target so the image of the target on the screen
is reasonably large and as sharp as possible.
➀ Is the focus of the image sharpest at its center or at its edges? (This is a subtle effect which is easier to
observe in a darkened room.) __________________________________________.
Place the Variable Aperture on the Component Holder as shown in Figure 12.2. The bottom of the V
formed by the Aperture plates should be aligned with the notch in the top of the Component Holder.
➁ Vary the size of the aperture. How does this affect
the focus of the image? ____________________
______________________________________.
➂ Explain your observations in terms of spherical
aberration. ______________________________
_______________________________________.
➃ What aperture size would give the best possible focus
of the image? Why is this size aperture impractical?
_________________________________________
______________________________________.
Data
Calculations
d
o
(mm)
d
i
h
i
1/d
i
+ 1/d
o
1/f
h
i
/h
o
-d
i
/d
o
500
450
400
350
300
250
200
150
100
75
50
Table 12.1
Figure 12.2 Using the Variable Aperture
Variable
Aperture
Spherical
Mirror