PASCO OS-8520 PHOTOMETER - Manual

Instruction Sheet
for the PASCO
Model OS-8520
PHOTOMETER
012-05631A
3/95
$1.00
Introduction
The PASCO OS-8520 Photometer is a non-electric com-
parative instrument which was designed as an accessory
for the OS-8515 Basic Optics System. The Photometer
base can stand on any flat surface for use with other optics
systems or for experiments not requiring an optics bench.
Equipment
The OS-8520 Photometer includes:
– Photometer with Base
– Set of Polarizers and Accessory Holder
– Neutral Density Filter Set which allows 25%,
50%, 75% and 100% transmittance.
Photometer
The PASCO OS-8520 Photometer operates in a similar
fashion to a wax photometer except the wax is replaced
by two high brightness fluorescent acrylic disks. By look-
ing through the eyepiece, students can see if the disks,
each receiving light from an opposite side of the photom-
eter, are equal in intensity. Although it is difficult for the
eye to determine relative intensities, it can detect equal
intensities quite accurately.
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© 1995 PASCO scientific
This instruction sheet written/edited by: Jon Hanks
A set of neutral density transmission filters (25, 50, 75,
and 100%) are included to be used on the Photometer to
block out a known amount of light so quantitative mea-
surements may be made. Note that because the Photom-
eter uses a fluorescent material, it will not respond
equally in the red and violet parts of the spectrum. This
Photometer was designed to be used with white light,
such as the PASCO Light Source (OS-8517). To de-
crease the intensity of the light that is emitted by the light
source, use a mask rather than decreasing the voltage to
the bulb. The use of a mask preserves the white color of
the light whereas a decrease in the voltage would change
the color of the emitted light to red.
A set of two mounted polarizers is also included. The
polarizer perimeters are marked in degrees and the
polarizers can be rotated to any angle to show the amount
of extinction of the transmitted light.
All the filters snap into the ends of the photometer and
can be rotated once they are snapped into place. The
polarizers are designed to fit on their own separate holder.
One polarizer can be snapped into each side of the holder.
How to Use the Photometer
To determine if the two sides of the photometer are illu-
minated by light of equal intensity, look down into the
conical eyepiece of the photometer. The cone is designed
to cast a shadow on the inner parts of the photometer to
allow a better view. Do not put your eye directly on the
eyepiece: keep your head at a distance which allows you
to comfortably focus on the orange indicator. If the light
is the same brightness on each side, the color and bright-
ness of the two sides of the orange indicator will appear to
be the same.
Polarizer
Eyepiece
Neutral Density
Filter