THE CHEMISTRY OF PHOTOGRAPHY
You haveprobablytakenmany pictures yourself, and posed for many more.
Have you ever wonderedaboutthe mysterious waythatphotographsaremade?
Once you know thenaturallaws on whichphotographyis based, the process
doesn'tseem so mysterious. Like all the wonders ofourage ofmoderntech-
nology, photography depends on knowing certain natural laws and then
puttingthem to work forourown purposes. Many of thenaturallawsthatwe
putto work in photographycomeunder the domainofphysics,andmore
especially,optics,the science of light. Optics teaches us how light rays behave
and how they are affected when they gothroughcertainkinds of lenses. This
knowledge is the basis for the designing of cameras.
The process of developing pictures, however, is essentially amatterof chemis-
try. The waythatlight affects and alterscertainchemicalcompoundsgives us a
means ofreproducingand preserving onpaperimages from real life. In the
following section, you will learnaboutsome of theunderlyingchemical pro-
cessesthatare essential tophotography.
HOW YOU CAN SEE THE EFFECT OF SUNLIGHT
ON HYDROGEN PEROXIDE
Gather thesematerials:Two testtubes;2 smalljars;somecellophanetape;
some blackconstructionpaper;hydrogen peroxide (H 202 ) ;2 uprightstands;
2 test tubeholders;2 wooden splints.
Follow this procedure:Cover one test tube completely (except themouth)with
blackconstructionpaper. Use thecellophanetape to fasten theconstruction
paperto the test tube. Also cover the outside of onejar.Fillbothjarswith
hydrogen peroxide. Fill the uncovered test tube withhydrogen peroxide, and
cover itsmouthwith yourthumb.Invertthe tube in thejarthatis notpaper-
covered. Push themouthof the tube aboutt inch below the surfaceofthe
hydrogenperoxide, and then fix the tube inthatpositionwith a test tubeholder,
attachedto anuprightstand.
Cutouta piece of black constructionpaperto fit over the surface ofthe
hydrogenperoxide in thepaper-coveredjar,and make a hole in the middle