Light leaving some source travels in straight lines, a phenomenon more formally called rectilinear propagation. We know straight-line paths because light casts shadows when blocked by opaque objects. (Actually, light bends around the edges of solid objects ever-so-slightly while exhibiting a property called diffraction which can be best explained by considering light to be a wave.) A fascinating consequence arises when we allow light from an object to to pass through a tiny pin hole and then fall on a reflective screen. In darkened room, an inverted image of the object appears on the screen. An early application of this phenomenon was called a camera obscura. Check this term on your favorite search engine; the result may prove interesting. Eventually, some clever scientist replaced the screen with a glass plate covered with an emulsion that decomposed in the presence of light, leaving a residue on the plate and thereby causing it to "remember" where the light had struck the plate. You will have an opportunity to study how modern cameras work in the optical instruments section of this site.
But for now, a curious side trip worth taking is a quest for the pinhole camera.
See pin hole cameras at these sites:
This page was last modified by mgosselin on 10/08/2005