Vernier Software and Technology
Vernier Software & Technology

Polarization of Light (Rotary Motion Sensor)

Figure from experiment 28B from Physics with Vernier


Perhaps you have seen a display of polarized sunglasses in a store. You can quickly test to see if the glasses are really polarized by looking through the lenses of two glasses and rotating one pair by 90º. If both pairs of glasses are polarized, the lenses will appear to go black. Why is that?

To explain the darkened lenses, we need to think of the light as an electromagnetic wave. An electromagnetic wave has varying electric and magnetic fields perpendicular to the direction the wave is traveling. This experiment focuses only on the electric field variation, represented by a vector. Light emitted from a typical source such as a flashlight is randomly polarized, meaning that the electric vector points in varying directions.

An ideal polarizing filter will remove all but the electric fields that are parallel to the axis of the filter. The light remaining is then said to be polarized. A second filter can be used to detect the polarization; in this case, the second filter is called an analyzer. The transmission through the second filter depends on the angle between its axis and the axis of the first filter. In this experiment you will study the relationship between the light intensity transmitted through two polarizing filters and the angle between the filter axes.

In the 1800’s Malus proposed a law to predict light transmission through two polarizing filters. The relationship is

I = I0cos2θ

where I0 is the intensity when the angle θ between the polarizer axes is zero. In this experiment, you will see if this law is useful in describing your polarizing filters.


  • Observe the change in light intensity of light passing through crossed polarizing filters.
  • Measure the transmission of light through two polarizing filters as a function of the angle between their axes and compare it to Malus’s law.

Sensors and Equipment

This experiment features the following Vernier sensors and equipment.

Additional Requirements

You may also need an interface and software for data collection. What do I need for data collection?

Physics with Vernier

See other experiments from the lab book.

1Graph Matching
2ABack and Forth Motion
2BBack and Forth Motion
3ACart on a Ramp
3BCart on a Ramp
4ADetermining g on an Incline
4BDetermining g on an Incline
5Picket Fence Free Fall
6Ball Toss
7Bungee Jump Accelerations
8AProjectile Motion (Photogates)
8BProjectile Motion (Projectile Launcher)
9Newton's Second Law
10Atwood's Machine
11Newton's Third Law
12Static and Kinetic Friction
13Air Resistance
14Pendulum Periods
15Simple Harmonic Motion
16Energy of a Tossed Ball
17Energy in Simple Harmonic Motion
18AMomentum, Energy and Collisions
18BMomentum, Energy and Collisions
19AImpulse and Momentum
19BImpulse and Momentum
20Centripetal Accelerations on a Turntable
21Accelerations in the Real World
22Ohm's Law
23Series and Parallel Circuits
25The Magnetic Field in a Coil
26The Magnetic Field in a Slinky
27Electrical Energy
28APolarization of Light
28BPolarization of Light (Rotary Motion Sensor)
29Light, Brightness and Distance
30Newton's Law of Cooling
31The Magnetic Field of a Permanent Magnet
32Sound Waves and Beats
33Speed of Sound
34Tones, Vowels and Telephones
35Mathematics of Music

Experiment 28B from Physics with Vernier Lab Book

<i>Physics with Vernier</i> book cover

Included in the Lab Book

Vernier lab books include word-processing files of the student instructions, essential teacher information, suggested answers, sample data and graphs, and more.

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Dev Reference: VST0660

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