Below is a picture taken of a sample from the Turtle Pond at Caltech, taken in the afternoon of Wednesday, April 10, 2019. The TA’s of my recitation section collected the sample that morning and brought it to section.

I plated the sample on a slide and used my foldscope to take a picture of the sample. However, there were no living organisms on the slide. I plated another slide to try to get something interesting, but that attempt failed as well. Finally, I used my foldscope to examine a slide from another student in the class, and while my foldscope was working, there still weren’t any living organisms.

The question I have regarding my picture is whether it is of a water drop or an air bubble. Since I put a decent amount of sample on my slide, there should be more water than air, so it would make sense if it were an air bubble. However, it looks more like a water droplet. If I still had the slide, I could examine it more deeply and see if I could determine the answer to my question.

I also would like to know why neither of my slides had anything on them. Since the sample was taken from the Turtle Pond, there should have been something on at least one of my slides. This might imply that the sample was faulty. To see if my sample was faulty, I would have to get another sample and plate that. However, other students who used water from the same sample were able to find organisms, so I may have simply been unlucky.

The magnification of my foldscope is 140x with 2 micron resolution from the 2.38mm lens.

#caltechbi1