PASCO OS-8539 Educational Spectrophotometer - Manual (Page 9)

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M o d e l N o . O S - 8 5 3 7 a n d O S - 8 5 3 9 S e t U p
5
You can find the wavelength of each color of light using the measured angle and the Grating spacing “d”.
m  = d sin m = 0, 1, 2…
where d is the distance between the
rulings on the Grating, m is the order
of the particular principal maximum,
 is the angle of the diffracted light,
and
 is the wavelength.
The Grating disperses the beam of
light into a first order spectrum and
higher order spectra. The higher
order spectra are broader and less
bright than the first order spectra, and
may overlap.
The Grating is blazed, so one side of
the spectrum is much brighter than
the other.
Set Up
This part of the manual describes how to set
up the Spectrophotometer System (see Fig. 3).
.
Mounting the Rotary Motion Sensor
This describes how to mount the Rotary
Motion Sensor to the hinge on the Spectropho-
tometer Base.
The top of the Spectrophotometer Base has a
short threaded post for centering the circular Degree Plate and for
holding the Grating Mount. It also has a magnetic pad for holding
the Degree Plate, and a triangular shaped index marker. One side
of the base has a post upon which the Pinion can be stored when it
is not in use. The other side has a spring-loaded hinge and two
small thumbscrews for mounting the Rotary Motion Sensor
(included in the Spectrophotometer System). On both sides of the
base are large thumbscrews and square nuts used for mounting
the Spectrophotometer Base on the Optics Bench (see Fig. 4)
The Rotary Motion Sensor has a three step pulley attached to its
shaft with a small thumbscrew. The sensor also has a rod clamp
attached at one end.
First, remove the small thumbscrew and three step pulley from
the Rotary Motion Sensor shaft. Then, remove the rod clamp
from the Rotary Motion Sensor (see Fig. 5).
Remove the two small thumbscrews from the threaded storage holes on the side of the Spectrophotometer Base
and set them aside for the moment. Remove the Pinion from the storage post on the opposite side of the Spectro-
photometer Base and set the Pinion aside for a moment (see Fig. 6).
GAIN
10 100
1
Figure 3: Spectrophotometer System (top view)
Collimating Slit
Collimating Lens
Diffraction Grating
Grating Mount
Light Sensor
Arm
Focusing
Lens
Aperture
Disk
High Sensitivity Light Sensor
Pinion Rotary Motion Sensor
Degree Plate
Light
Source
Optics Bench
Figure 4: Spectrophotometer Base (top view)
Hinge
Large
Thrumb
screw
Small
Thrumb
screws
Magnetic Pad
Pinion
Index
Threaded Post
Figure 5: Prepare Rotary Motion Sensor
Thumbscrew
Three-step Pulley
Rotary Motion Sensor
Rod Clamp