# Lab 5: --Polarization Lab

Problem: What is the relationship between how much light passes through a Polaroid filter and the angle the filter is rotated?

Materials: One Polaroid filter, one set of Polaroid glasses, photocell, light source, protractor, ring stand, various clamps.

Procedure:

1) Begin by investigating some of the properties of light. Look at a your lab table and observe how light reflects off of it.

2) Look through the single Polaroid filter at a light bulb. Rotate the filter. Observe and record any changes in your lab notebook.

3) Look at the light reflected off your lab table or any shiny surface. Now look at the same light through the Polaroid filter. Rotate the filter slowly. Continue to rotate a complete 360 degrees.

4) Discuss what you observe with your lab group.

5) Set up your experiment as shown in Figure 1.

6) Copy Table I into your lab notebook.

7) Turn on the light source.

8) Set the protractor to 0 degrees and record the intensity of light passing through both filters. Record the value in Table I.

9) Turn the filter 20 degrees and measure the light intensity. Record your value. Continue until you have completed 180 degrees.

Results:

Table I.

Angle Light Intensity

0

20

40

.

Graph: Plot the angle (degrees) on the x-axis and the intensity (milliamps) on the y-axis.

Discussion:

1) What are the independent and dependent variables?

2) How are the variables changing with relationship to each other?

3) What happens to the dependent variable when the independent variable increases? decreases?

4) How does the relationship shown in this experiment compare with other relationships you have so far seen?

5) How does the equation for this relationship compare with those of other equations you have studied?

Applications:

1) Why are Polaroid glasses recommended for people driving cars? Where else would Polaroid filters come in handy?

#### What are Mathematical Relationships

What is a mathematical relationship and what are the different types of mathematical relationships that apply to the laboratory exercises in the following activities.

#### Labs

Lab 1:    The Spring Constant  -- Problem:  What is the relationship between how much a spring stretches and the force pulling on the spring?

Lab 2:    The Pendulum  --Problem: What is the relationship between the period of a pendulum and the length of the string of  the pendulum?

Lab 3:   Mass, Volume and Density--   Problem: What is the relationship between the mass of a ball and its volume assuming a constant density?

Lab 4:   Light Intensity--  Problem: What is the relationship between the intensity of a beam of light and the distance from a light source?

Lab 5:   Acceleration--  Problem: What is a the relationship between how the distance travels and the time in travel for an accelerating object?

Lab 6:   Polarization --  Problem:  What is the relationship between how much light passes through a Polaroid filter and the angle the filter is rotated?

Lab  7:   Ohms Law--  Problem:  What is the relationship between current, voltage when there is a constant resistance in an electric circuit.

Lab 8:   Radioactive Decay-- Problem: What is the relationship between the decay of radioactive material and the time allowed for the decay?

Lab 9: Water Pressure-- Problem: What is the relationship between water pressure and depth of water?

Lab 10: Attractive and Repulsive Forces--   Problem: What is the relationship between the distance between two magnets  and the force between them?

Lab 11: Damping Motion--  Problem: What is the relationship between the height a ball bounces and the number of times it has bounced?