# Calculating Intensity of Light from Potential Difference

• ausdreamer
In summary, the conversation discusses a problem with an experiment involving a diode LASER and polarizers to demonstrate Malus's Law. The group used a photo detection device and an Oscilloscope to measure changes in potential difference, but are unsure how to calculate the intensity of the photon beam. Malus's Law states that the intensity is directly proportional to the potential difference over the detector, and the group just needs to state the potential difference as the intensity. The formula for Malus's Law is I = Io cos^2(theta), where I is the intensity, Io is the maximum intensity, and theta is the angle between the polarizers.

## Homework Statement

It's a problem I'm having with my experiment.

We set up a diode LASER through 2 polarizers, and changed one of the polarizers' angle with respect to the other, to demonstrate Malus's Law. We used some sort of photo detection device (which we were told uses the photoelectric effect to measure intensity of light) which was connected to an Oscilloscope which measured the change in potential difference over the detector. SOMEHOW we are expected to calculate the intensity of the photon beam from the potential difference measurements.

## Homework Equations

Well all I know is that the potential difference over the detector is directly proportional to the intensity of the photon beam passing through the 2 polarizers.

## The Attempt at a Solution

What does Malus's Law say? How do you need to plot your measured quantities in order to verify it?

I spoke to my tutor about my problem and he was confused why I wanted to know the intensity after we'd measured the potential difference. This is because the potential difference is directly proportional to intensity of light (in our experiment) and so we just needed to state the potential difference the LASER made as the 'intensity'.

Just for your own interest, Malus's Law states:

I = Io cos^2 (theta)

Where I is the intensity of light getting through the two polarisers, Io is the maximum intensity if no polarisers are present and theta is the angle the 2nd polariser makes with the 1st polariser. :)

## 1. How do you calculate the intensity of light from potential difference?

The intensity of light can be calculated by using the formula I = V/d, where I is the intensity of light, V is the potential difference, and d is the distance between the light source and the point where intensity is being measured.

## 2. What is the unit of measurement for intensity of light?

The unit of measurement for intensity of light is watts per square meter (W/m2).

## 3. Can the intensity of light be calculated for all types of light sources?

Yes, the intensity of light can be calculated for all types of light sources as long as the potential difference and distance are known.

## 4. How does increasing the potential difference affect the intensity of light?

Increasing the potential difference will result in a higher intensity of light, as the energy of the electric field is directly proportional to the potential difference. This means that a higher potential difference will result in more energy being transferred to the light source, increasing its intensity.

## 5. Is there a minimum potential difference required to calculate the intensity of light?

No, there is no minimum potential difference required to calculate the intensity of light. However, a higher potential difference will result in a more accurate calculation of the intensity of light.