The Saturday Scientists


The Mini Maglite, with its tiny high intensity bulb, makes a great light source for exploring and understanding shadows. The small size of the filament in the bulb allows it to throw very sharp shadows. To use the Mini Maglite for shadow effects, remove the entire reflector assembly, leaving the bulb exposed. This also turns the light on, so you'll have to re-install the reflector or remove the batteries to turn the light off.

The shadow demonstration is performed as follows: gather together a collection of objects you think will have interesting shadows. Some of my favorites are wire sculptures and geometrical or mechanical models made with one of those modeling sets. Dried flowers can also be interesting, if they have a lot of branch-like structure.

Dim the room, and remove the reflector from the Mini Maglite. Stand near a plain white wall or screen and place the object to be explored between the maglite and the wall or screen. Explore the object by probing it with the Maglite lamp, and observing the shadow cast onto the wall. The shadows will expand and move in perfect three dimensional perspective as the flashlight moves around and through the object. If you want to demonstrate geometrical concepts, you can use a piece of quarter-inch wire mesh. Try to discover the relation ship between the lamp-to-mesh distance (holding the mesh-to-screen distance constant) and the size of the projected square shadows. The wire mesh also gives a great 3D motion effect if held edge-on to the screen as the light "flies" over it.

3D Shadows

There is something else you've got to try. Get two Mini Maglites, and some red and blue cellophane. Wrap the bulb of one light in red cellophane, and do the same to the other one with the blue. Find or make a pair of red/blue 3D glasses with red cellophane in one lens and blue in the other. Hold the two flashlights with their bulbs very close together and explore objects as before. The lights will throw red and blue shadows, which give remarkable 3D images when viewed with the glasses! [Diagram]

In some cases you can get a good three dimensional effect by doing the following: Remove one of the lenses from a pair of sunglasses. With a single Mini Maglite illuminating an object, rotate the object slowly and steadily, making a regularly changing shadow. Or use an object that is motorized, such as a model built with a construction set. If conditions are right, i.e. if the maglite battery is fresh and the remaining lens of the sunglasses is not too dark, the shadow of the rotating object will appear three dimensional. This occurs because lowering the intensity of light to one eye with the sunglass lens delay's the brain's processing of the image from that eye. So the result is that two images from slightly different perspectives are combined by the brain - exactly what is required for stereoscopic or 3D vision!

COPYRIGHT © 2000-2021, Brian Wesley Rich

Updated 26 January, 2021

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