Light Intensity & Stepper Motors
Recommended for grades 9–14.
Introduction
Light is an electromagnetic wave composed of alternating electric and magnetic fields. Light sources, such as flashlights, emit electromagnetic waves with electric fields that oscillate in all different directions. This type of light is called unpolarized light. There are multiple ways of separating out light whose electric fields have the same plane of oscillation. The most common is the use of polarizing filters. Polarizing filters are plastic sheets that have many aligned long-chain molecules embedded in them. When unpolarized light passes through these sheets, only the light with electric fields parallel to the long-chain molecules will pass through. Almost all other electromagnetic waves will be absorbed by the sheets. The filtered light is said to be polarized. When two polarizing filters are stacked in alignment, they transmit almost as much light as a single filter. However, as one polarizing filter is rotated relative to the other, less light passes through, and the intensity of light decreases. When one polarizing filter is rotated until it is perpendicular to the other, very little light will pass through.
Objectives
Build a device to rotate a polarizing filter using a stepper motor and the Vernier Digital Control Unit (DCU), and then write a LabVIEW program to graphically display the light intensity from a Vernier Light Sensor as the filter rotates through 360°. Your Waveform Chart should be scaled appropriately to display the entire range of light intensity for your apparatus. Place a control on the front panel to allow the user to vary the speed of the rotating filter.
Sensors and Equipment
This project requires each of the following Vernier sensors and equipment (unless otherwise noted):
Additional Requirements
You will also need a SensorDAQ interface and LabVIEW software for data acquisition.
Download Experiment Preview
The student-version preview includes:
- Step-by-step instructions for computer-based data collection
- List of materials and equipment
The preview does not include essential teacher information, safety tips, or sample data. We strongly recommend that you purchase the book for classroom use.
Standards Correlations
No standards correlations for this experiment.
Experiment 6 from Engineering Projects with NI LabVIEW and Vernier Lab Book
Included in the Lab Book
Vernier lab books include a CD with word-processing files of the student instructions, essential teacher information, suggested answers, sample data and graphs, and more.