The concept of polarization can be used to measure light intensity using a device known as a polarizer, and the principle is based on how light behaves when passing through polarizing filters.
Here’s how it works:
- Unpolarized Light: Natural light consists of waves vibrating in all directions perpendicular to the direction of travel.
- First Polarizer (Polarizing Filter): When unpolarized light passes through a polarizer, only the component of the light wave vibrating in a specific direction (say vertical) is allowed to pass. This results in linearly polarized light.
- Second Polarizer (Analyzer): A second polarizer is placed after the first, but it can be rotated. The intensity of the light emerging from this second polarizer depends on the angle between its axis and the axis of the first polarizer.
- Measuring Intensity:
- When the two polarizers are aligned, maximum light passes through, and intensity is highest.
- When they are at 90° (crossed), no light passes through, and intensity drops to zero.
- By rotating the analyzer and measuring the transmitted light intensity, one can determine the polarization angle and use that information to calculate the original intensity.
- Applications:
- Polarimeters measure light intensity in chemistry and optics.
- Photography light meters use polarization to estimate brightness.
- In material stress analysis, polarized light intensity helps identify stress patterns in transparent materials.
So, polarization acts as a filter to control and measure how much light gets through, thereby giving a method to measure light intensity indirectly.