The honest cheat
I've been thinking about the last of the first year activities on the wave nature of light. I wanted to make an activity where the students would use the colour picker tool in paint.net to measure the brightness the different bands in a photograph of single slit diffraction pattern. If it's red light then measuring the R value should do the trick. I downloaded the programme and reminded myself how to use the colour picker. I then selected a photo from the internet and started measuring. The problem is that the laser light is so bright the whole central maximum is maxed out so you get a flat top then a far to big first max (it should be about 1/20 th of the size of the central one). So I wondered if I could cheat.
I already have a GeoGebra single slit simulation so used it to produce red spots that had an R value that was proportional to the intensity in the diffraction pattern. I put the spots together in paint, blurred them in paint.net and got this.
There are subsidiary maxima on either side of the central max but they are too dim to see.
Using the colour picker tool I analysed the pattern, put the data into LoggerPro, fitted a best fit curve and arrived back at the beginning. I will get my students to do analyse the pattern but I'll tell them how I faked it. It's OK to cheat if you admit it isn't it? Alternatively I might try and get a very dim photo of the real thing. If anyone has one please send it to me and I'll use it.