How Intense is Light?

Not exactly how it looks like, but this shows how the experiment was done.

So here's the very first experiment my groupmates and I did for the year 2012! :)

It was very simple. We connected a light sensor to LabQuest and then measured the light intensity in lux of the  light from a source with respect to the sensor's distance from it. At first the readings were the same (~1cm to 14cm) until at 15cm, the light intensity reading dropped, and so on until it became constant. This constant reading is said to come from the environment and must have been set to zero.

We had many questions for this experiment: Why did the light intensity became constant? Was the light sensor's minimum reading supposed to be not zero? Did we note a wrong set of data?

Somehow, these questions made sense as we discussed how to write this paper. For the previous technical reports we did, we always cut the parts of the report to each member and then compile them on the end of Sunday. This lead to my incomprehension of the previous experiment we did (the one with PV diagrams). It was nice to do this change, and it was never too late.

Going back to the experiment, we analyzed the data by plotting the points and taking an exponential trendline. We had a nice graph, however we obtained a 10% deviation from the accepted value.

There were some trivial things I learned in this experiment.
1) W/cm^2 is a unit for irradiance and lux is a unit for illuminance (http://www.vernier.com/til/413/)
2) The light sensor we used is optimized for visible light only, much like our eyes.
3) Illuminance is different from light intensity, as well as luminous flux.