A few days ago I showed the early results for the spectroscopy demonstration I’m working on for my instrumental analysis class. I passed scattered light and collimated light (using an educational kit from Amazon) through a diffraction grating (also from Amazon) and showed that the results were very different. I posed the question in my vlog for my students: why does the scattered light show up as an image of a rainbow while collimated light shows a rainbow projected onto the paper in front of the grating?

Here’s the answer (if you don’t want to watch the answer in video form). collimated beams create a set of collimated rays of different colors which scatter from the paper.

Scattered light can be seen at different angles through the diffraction grating from the same location, so looks like an image of a rainbow.

For a more thorough explanation, I hope you’ll check out the video.

In other news, a Science News report brought my attention to a hand centrifuge capable of 100,000 rpm. The original paper in Nature from the Prakash lab at Stanford is everything I love about open source science. It’s thorough, beautifully presented, and easily replicable.