PASCO OS-8520 PHOTOMETER - Manual (Page 6)

6
Photometer 012-05631A
Procedure
➤ NOTE: You may want to cover the crossed-arrow objects on each light source to reduce
the excess light in the room. The room lights must be off for this experiment.
➀
Set the neutral density filter for 100% transmission.
➁ While looking into the photometer’s conical eyepiece, adjust the position(s) of the light
source(s) until the two sides of the orange indicator have equal intensity.
➂ Set the neutral density filter for 75% transmission.
➃
While looking into the photometer’s conical eyepiece, rotate the label-side polarizer until the
two sides once again have equal intensity. Record the angle in Table 2.1. Rotate the polarizer
back to zero and repeat the measurement two more times.
➄ Repeat the previous step for 50% and 25% transmission.
Table 2.1: Data and Results
% transmittance 75% 50% 25%
trial 1
trial 2
trial 3
Average angle
φ
cos
2 φ
% difference
Analysis
➀
For each of the neutral density filter settings, calculate the average of the three trials and
record the average angle in Table 2.1.
➁
To calculate the predicted percentage transmittance for each case, calculate the square of the
cosine of each average angle and record in Table 2.1.
➂
Calculate the percent difference between the percentage transmittance and the predicted value
for each case and record in Table 2.1.