IOT Hackathon: Graph of light waves

We want to make a project in which we want to sense the light waves and get its graph on screen.
help us to start and go through the project.

At the the simplest level youll need to repeatedly fetch values from sensors using something like setTimeout and use one of the libraries from here http://thenextweb.com/dd/2015/06/12/20-best-javascript-chart-libraries/