# How Can I Accurately Measure Light Intensity After Polarization?

• ellion71
In summary, part of the independent investigation involves carrying out an experiment to confirm Malus' Law. This will involve using a bulb as the ambient source and two polarizing lenses, and measuring the intensity of light after polarization. By graphing the angle of the analyzing polarizer against intensity, a Cosine curve is expected to be obtained. However, there is uncertainty on how to measure the intensity of light after polarization. The lecturer has suggested using an irradiance detector, which measures in LUX, but it is not necessary to convert this value to W/m^2 as the ratio of intensity after polarization to the intensity before polarization is sufficient to confirm Malus' Law. Any help or advice would be appreciated.
ellion71
Part of my independant investigation requires me to carry out an experiment, which when I graph results, would confirm Malus' Law.

I plan on using a bulb as my ambient source and two polarizing lenses. I will then measure the intensity of the light after polarization. Hopefully, if i graph the angle of the analyzing polarizer against intensity I will get a Cosine curve.

However, I am not quite sure on how to measure the intensity of the light after polarization.

Any help/advice would be much appreciated.

P.S
My lecturer has suggested using a irradiance detector which measures in LUX but I am not sure how to convert a value in LUX to a value in W/m^2.

You don't need to convert. The ratio of the intensity after the polarizer to the ratio of the intensity before the polarizer is all you need to know in order to confirm Malus' Law.

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I would suggest using a photometer to measure the intensity of light after polarization. A photometer is a device specifically designed for measuring the intensity of light in a specific direction. It works by converting the light energy into an electric current, which can then be measured and converted into units of power per unit area (such as W/m^2). This measurement will provide a more accurate and precise result compared to using a simple bulb and polarizing lenses.

Another important factor to consider in your experiment is controlling for external factors that may affect the intensity of light, such as ambient light or temperature. You may need to conduct the experiment in a controlled environment to ensure accurate and consistent results.

Additionally, to confirm Malus' Law, it is important to vary the angle of the analyzing polarizer and record the corresponding intensity values. This will allow you to plot a graph and observe the expected cosine curve, which confirms the law.

In conclusion, using a photometer and controlling for external factors will help you accurately measure the intensity of light after polarization and confirm Malus' Law. I hope this advice helps and wish you success in your experiment.

## What is Malus' Law?

Malus' Law is a scientific principle that describes the relationship between the intensity of light before and after passing through a polarizer. It states that the intensity of light after polarization is directly proportional to the square of the cosine of the angle between the polarizer and the direction of the incoming light.

## What is the purpose of measuring the intensity of light after polarization?

The purpose of measuring the intensity of light after polarization is to confirm the validity of Malus' Law and to understand the behavior of polarized light. This can help in various fields such as optics, astronomy, and telecommunications.

## What equipment is needed for experiments to confirm Malus' Law?

The equipment needed for experiments to confirm Malus' Law includes a light source, a polarizer, a detector to measure the light intensity, and a device to rotate the polarizer. The light source can be a laser, LED, or any other source of polarized light.

## What are the steps involved in conducting experiments to confirm Malus' Law?

The first step is to set up the equipment and make sure the polarizer is aligned with the light source. Then, the polarizer is rotated at various angles while measuring the intensity of light using the detector. The data is then analyzed and compared to the expected values based on Malus' Law.

## What are the potential sources of error in measuring the intensity of light after polarization?

Some potential sources of error in measuring the intensity of light after polarization include inaccuracies in the equipment, ambient light interference, and human error in aligning the polarizer and taking measurements. It is important to control these factors and take multiple measurements to ensure accurate results.

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