Electronic Structure and Periodic Trends Lab

I don't exactly see the point of the lab to be honest. I spent the entire hour adjusting a little knob that with the slightest twitch will jump up past what I need it at. Me and Matt shared our machine with another group and so I really should be trying to understand what the meaning behind the lab is, but I really don't feel like it. This entire paragraph is just afiller and Ihave no idea what to say about this lab except I should be trying to understand it. It was just testing different substances on how they respond to light. Anyway here is a picture:

Stuff is happening