The light gate and light sensor. The light gate has a continuous beam to its sensor.
The light sensor (or luxmeter) measures the amount of light falling onto its sensor.
A closer view of these sensors

The pendulum swinging between the sensors. Here it will break or interrupt the light beam between the light gate. It will also decrease the amount of light falling on the luxmeter.
2
The interface and the sensors are plugged into this device which is then connected directly to the laptop computer.
2004

This is a distance or motion sensor. It uses an ultrasonic beam to measure the distance between its sensor and an object. The beam must be reflected off the object and back onto the sensor for it to work accurately.
A view of the experimental set-up from behind the light gate and luxmeter.

The same view to show the overhead projector being used as a strong light source to illuminate the luxmeter. The sensors are plugged into this device which is then connected directly to the laptop computer.
4
A side view of the distance sensor at a height to measure the distance between the pendulum and sensor.
2004

A screen shot of the data being recorded by the sensors. The first column is time, the second is the luxmeter (light intensity) and the third is the percentage (%) reduction of received light.
A graphics calculator that is attached to the motion sensor

A screen shot of some processed results on the laptop computer.
6
A screen shot of the raw data as it is recorded on the computer. Note the periodic relationship between the light intensity (lx) / light gate and the percentage reduction of received light.
2004

A screen shot of some processed results in an Excel worksheet. Again, note the matching of reduction in light intensity and the increased light received.