PASCO OS-8500 INTRODUCTORY OPTICS SYSTEM - Manual (Page 70)

Introductory Optics System 012-02744K
®
64
Exp 17: General Diffraction
Exp 18: Introduction to Optical Instruments
➀
A virtual, magnified image is formed for object
distances of less than the focal length of the lens.
➁
A real, magnified image (also inverted) is formed
for object distances between one and two focal
lengths from the lens.
➂
A real, reduced image (still inverted) is formed for
object distances greater than twice the focal length
of the lens.
➃
Any real image can be focused on the screen, thus
any object distance greater than the focal length of
the lens will work.
Suggestions on – Procedure
➀
Smaller apertures make the diffraction pattern more
clear.
➁
Smaller apertures make the diffraction pattern less
bright.
➂
White light causes many overlapping diffraction
patterns of different colors and slightly different
sizes. Color filters simplify this pattern by limiting
the pattern to one color.
Crossed Slits
➀
There are really two diffraction patterns at 90° to
each other, caused by the two slits. This is impor-
tant for the other parts of the lab; each diffraction
pattern is independent of the others.
Random array of Circular Apertures
➀
The diffraction pattern is wider when the holes are
smaller; just as in part 1 of experiment 16.
➁
The diffraction pattern of a point source through a
circular aperture is symmetrical because the aper-
ture itself is symmetrical. Diffraction effects are
most pronounced in a direction parallel with the
smallest dimension of the aperture; but in a circular
aperture, all directions are the same.
Square array of Circular Apertures
➀
This pattern is similar in that there is an overall
“target” pattern. It is different in that the target is
made up of a square grid of points, roughly like so:
➁
–
➃
Drawings will vary.