Teaching Guide:

This WebQuest is designed to introduce students of a variety of backgrounds (science or art) to the essentials of the photographic process. Although the stranding part may be interpreted as being rather far-fetched, the knowledge gained can be used to actually create totally do it yourself photographs, an anomaly in this digital age.

There are two phases to this WQ; the fabrication of the camera and the production of the light–sensitive materials. It would be best that there are teams of at least two, so that the students can concentrate on one or the other essentials.

It really would be possible to pull off this scenario. A camera needs to be only a light tight box, and no lens is necessary, only a pinhole less than a millimeter in diameter will provide an acceptable image. Chemical photography revolves around using metals, particularly silver compounds to form the image, but plant matter could be used to make pigments that bleach under exposure to light. (Anthotypes)

The Physics Aspect:

Short of having a camera being ship-wrecked along with the survivor, there are other optical devices which could yield lenses or mirrors that could form suitable images. The research the student does will reveal that some lenses are not suitable for producing images, i.e. the lenses in the typical eyeglasses, for the correction of myopia, will not focus an image onto a target. However, glasses designed for reading or hyperopia would be satisfactory.

There could be other optical devices that could be used, like the objective lenses from telescopes or binoculars, which conceivably could be part of the flotsam from the wreck. Even the lens from a CD player could be used once the batteries run down.

Similarly there are mirrors that could be used to form an image, not convex rear view mirrors or flat bathroom mirrors, but magnifying mirrors for shaving or cosmetics could be utilized. And as mentioned above, a small hole could be used, and the research the student does would show how to find the optimal size of the pinhole.

This phase of the project tests the students’ ability to do the research to see what is required, and uses their ingenuity in applying the research to finding solutions to the fabrication of the camera, like using logs or coconuts for the camera body. Going even deeper, they could find that it isn’t all that hard to make a lens, as glass is simply melted sand, and there is plenty of that. The sand could also be used as a grinding compound to shape the lens. (We’re talking about an infinitely long time to kill.)

The Chemistry Aspect:

This second phase is the harder part, as some of the necessary chemicals might not be available. Compounds of silver, namely silver chloride, silver bromide, and silver iodide are the typical light-sensitive crystals. There would be plenty of salts to provide the chlorine in sea water, but the silver could be a problem. Recipes call for silver nitrate to be mixed with the salt, and part of the WQ should investigate sources of it (AgNO3 is used as an antiseptic, and might be found in a medical kit!) or how to make it. (Industrially it is made by dissolving silver in nitric acid, but another useful silver salt could be made by dissolving some jewelry in an acid found on the island, like citric acid found in fruit!)

There are other alternative processes using iron or chrome as the metal in the light reaction, so a similar search could be performed first for the recipes, and investigating the likelihood of finding the chemicals or how to prepare them.

Students’ ingenuity is needed for figuring out the substrate for the images. Bark, leaves, hides, etc. could be used, but some wiser ones might figure out that plenty of paper could be made from the trees of the island. The grading rubric reflects the deeper thinking.

If there are no qualms about using chemicals in a classroom, the students could actually build their camera’s design and make exposures to prove that they were on the right track!

Estimated time of completion of this WebQuest would be approximately 10 classroom hours, without making any exposures.

Previous:

Introduction: http://cuip.net/~ewesly/WebQuest/Introduction.htm

Task: http://cuip.net/~ewesly/WebQuest/Task.htm

Process: http://cuip.net/~ewesly/WebQuest/Process.htm

Resources: http://cuip.net/~ewesly/WebQuest/Resources.htm

Evaluation: http://cuip.net/~ewesly/WebQuest/Evaluation.htm

Conclusion: http://cuip.net/~ewesly/WebQuest/Conclusion.htm