User's Manual

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

% 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.