### Experiment 2 − Intensity over distance

The Intensity over distance experiment has as task to measure the power from the light sources with a given distance and a fix step size.

#### General description

From the theory is known that the energy which is radiated outward radially in three-dimensional space from a source is inversely proportional with the square of the distance from the source.
This process is known as the Inverse square low. More information can be found at the following link Inverse-square Law.

#### Experiment Sequence

For a better understanding of how the experiment works, the light bulb was again chosen as example.

To perform the experiment, the user has to follow the next steps:

1. Select the “Intensity over distance” tab from the upper part of the plot.
Wait until the input and output parameters specific for the experiment will appear.

2. Choose a light source by pressing the “Choose a light source” control (example: Light bulb).

3. Select the step at which the sensor should make measurement “step size” control (example: 100) and interest distance up to which the sensor should take measurements, by pressing the “maximum distance” control (example: 1000).

4. Next step will be to choose the sensor by pressing the “Choose a sensor” control (example: photodiode sensor).

5. Change the intensity of the light by mowing the pointer from the “Power of the light sources in percentage” pointer slide (example: 100).

6. Press the “Start batch” button to starts the measurements.
The input parameters cannot be change when the batched lab is running.
The system will start to take measurements which will be displayed on the plot from the left side.

In the figure above can be seen the radiation power emitted by a light bulb over distance which was measured with the three sensors.

Since the light represents a form of electromagnetic radiation, this decreases in intensity the further it travels from the emission point. The Invers square law is use to predict the rate of illumination of a light source.

#### Exercises/Questions

I. How the different light sources behave over distance (measurement with the same sensor)?

II. Which are the differences between the characteristics of a light source for different sensors?

III. Find the differences between a light source and the heater element.