Experiment 07 · Setup Diagram

Malus Law

Nothing to wire but the photo cell and its meter. Everything else on this bench is optics in a straight line, and the only thing that matters is that all of it sits at the same height.

Procedure

1. 1.

   Arrange the apparatus as shown in the figure above.

2. 2.

   The source O, the convex lens L, the polarizer P, the analyzer A and the window of the photo-voltaic cell must all be at the same height, so the light travels straight down the axis of the bench.

3. 3.

   Switch ON the incandescent bulb.

4. 4.

   For any orientation of the polarizer P, rotate the analyzer A until the deflection in the microammeter is a maximum. Note the position of the analyzer on the circular scale and the corresponding deflection. This position of the analyzer is θ = 0°.

5. 5.

   Rotate the analyzer through a small angle, say 10°, and note the steady microammeter deflection.

6. 6.

   Repeat by rotating the analyzer through 10° each time and noting the corresponding deflection, until it becomes practically zero.

7. 7.

   Calculate cos²θ for every angle recorded, and plot the readings:

   I = I₀ cos²θ