PASCO OS-8500 INTRODUCTORY OPTICS SYSTEM - Manual (Page 67)

012-02744K Introductory Optics System
®
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Spherical Aberration
➀
The image will be sharpest at the center.
➁
Smaller apertures make the image sharper, but
dimmer.
➂
Smaller apertures limit the light to the central por-
tion of the mirror. Using a smaller part of the
spherical mirror causes smaller amounts of spheri-
cal aberration.
➃
The best aperture for maximum sharpness would
be a pinhole. This is not practical, though, because
it limits the amount of light entering the mirror and
causes diffraction.
Exp 14: Spherical Lenses-Spherical and Chromatic
Aberration, Aperture Size, and Depth of Field
Spherical Aberration
➀
The focus becomes sharper as the aperture is de-
creased.
➁
The best image focus would be obtained with the
smallest possible aperture. This is not practical,
however, because smaller apertures allow less light
to enter; and at very small apertures, diffraction de-
grades the image.
Depth of Field
➤ ➤ ➤ ➤ ➤Note: The depth of field measured by students
will vary, depending on what they consider
“good focus”.
➀
The depth of field increases as the aperture is de-
creased.
➁
An infinite depth of field would require an aperture
size of zero.
Exp 13: Image Formation with Cylindrical Lenses
Focal Point
➀
F.L. 1 = 43 mm
F.L. 2 = 31 mm
➁
The refracted rays are parallel when they go
through the center of the lens, but are not parallel
when they go through the edges.
➂
Same as #2
➃
Because of the shape of the lens, it bends the light
at only one edge - the curved one. When the lens is
rotated 180°, the curved side of the lens is on the
opposite side, so the refraction occurs at a different
place.
Image Location
➀
57 mm from the lens
➁
As you decrease the object distance, the image dis-
tance increases.
➂
Yes, but it is a virtual image located on the oppo-
site side of the lamp from the lens.
Magnification & Inversion
➀
The magnification decreases with object distance.
➁
The image is inverted for all object locations
greater than the focal length of the lens.
Cylindrical Aberration
➀
The rays do not all focus at the same point.
➁
Make it thinner, decrease the curvature, limit the
aperture to include only the center of the lens,
change the shape from circular to parabolic. (An-
swers may vary.)