Question

You have an experimental setup consisting of a light source, three polarization screens, and a light sensor. Logger pro records the intensity [lux] of the light incident to the light sensor vs. the angle of the polarization screen. The initial intensity of your light source (no polarizing screens) is  = 784 lux. Assume zero ambient light during the entire experiment.

a) (4 pts) If you place ONE polarizing screen between the light source and light sensor, what is the expected intensity measured by the light sensor?

=                                                                       

b) (6 pts) Now you add another polarizing screen between the light source and the light sensor, TWO total. You collect data by recording the intensity vs. the angle of the second polarizer for a full 360 degrees. How many maximum intensity values should the plot have? Approximately at what angle values are they located?

c) (10 pts) From our experimental step up in part b), you create a plot of  vs. . What values would you expect the slope, , and the intercept, , of this plot to be? Don't include uncertainties.

Answer 1

a) The intensity after the polariser varies according to Malus law:

where is the incident intensity it is given in this problem as 784 lux

Thus,

b)

The intensity after the second polarizer is obtained by treating I_1 as the incident light in the Malus law:

keeping the first angle constant, if the second angle is varied, we get 3 maxima.

similarly, if the second is kept constant and the first is varied, we again get 3 maxima.

But, in the entire range of theta_1 and theta_2, we would get the maxima only when theta 1 = 0, 180, 360 and theta_2 = 0, 180 , 360.

So, there will be 9 maxima in total.