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