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Polarization of Light: Intensity Variation

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3. You view light from a flashpoint through a Polaroid. Describe any intensity variation as the Polaroid is rotated. Explain your answer.

Describe any intensity variation as the flashlight is rotated.

4. Unpolarized light travels through two pieces of Polaroid as shown below.

When the two Polaroids are rotated to 0 degrees as shown, the transmitted intensity is I_0. What percentage of I_0 will be transmitted when the analyzer is rotated to 30 degrees? Show your calculation.

https://brainmass.com/physics/intensity/polarization-light-intensity-variation-392349

SOLUTION This solution is FREE courtesy of BrainMass!

As the light from the flashlight is unpolarized the intensity is corresponding to oscillation of electromagnetic fields distributed uniformly in all direction in the plane perpendicular to the direction of light rays. After passing through the Polaroid only the oscillations parallel to the axis of Polaroid are passed through it and thus the transmitted light is polarized and there is decrease in intensity of transmitted light to half of its original value.

Now if the Polaroid is rotated, the axis of polarization rotates but still the intensity of transmitted light will be half of the intensity of incident unpolarized light, it will not be affected by rotating the Polaroid as the incident light is still unpolarized.

In this case the unpolarized light rotates and makes no difference in the incident beam. There will be no variation in the intensity of transmitted Polarized light is observed as it remains half that of the incident light. The axis of polarization remains unchanged.

The beam gets polarized after it passes to first Polaroid which acts as polarizer. After transmission from the first polarized the intensity of the polarized light is I0. Now if the second Polaroid which acts as analyzer, is having its axis in the same direction as the axis of polarizer ( = 0), all the vibrations are allowed by the analyzer and thus the intensity of the light transmitted through the analyzer will be same as that of the intensity of the polarized light incident on it i.e. I0.
If the second Polaroid which acts as analyzer, is now rotated by 900 will have its axis perpendicular to the axis of polarizer ( = 900), all the vibrations are blocked by the analyzer and thus the intensity of the light transmitted through the analyzer will zero. Thus the percentage of intensity of the transmitted light will be zero percentage.

If the angle between the axis of polarizer and analyzer is q and the intensity of the light from polarizer is I0, the intensity I of light transmitted through analyzer is given by law of Malus as

Now if the analyzer is rotated by 300 the intensity of the transmitted light is given by

Thus the percentage of transmitted intensity will be 0.75*100 = 75 %.

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