Mixing Light Colors with the Three Port Light Source


Marty SagendorfBy: Martin Sagendorf

We see hundreds of colors, but the colors we think we see are often not what we’re actually seeing – i.e. many of these colors are combinations of other colors.  ‘Light’s Story’ is fascinating and full of surprises.  It begins with knowing that radiating and re-radiating substances emit light.  The light colors emitted are functions of a number of factors: the substance, or the incident light, or the temperature of an incandescent source.

All the textbooks explain ‘additive’ and ‘subtractive’ colors.  Explanations are fine, but actual experience makes both an immediate impression and a very lasting learning experience.  For example, here’s how only RED, GREEN, and BLUE light colors combine to produce two new unexpected colors.

Mixing Light - Educational Innovations

But we’re getting ahead of ourselves… let’s start with something we’re really familiar with: pigment colors.  We all know that mixing different paint (pigment) colors will produce new colors.  For example, when we mix red and green pigments we ‘see’ brown. And, as everyone knows, mixing a wide range of pigment colors will produce the ‘color’ we see as black.  But, odd things happen when we mix two light colors.  We don’t get the same color that we obtained when we mixed pigments.

When we mix red and green light colors we don’t ‘see’ brown: we see yellow!  How can this be?  Then… even though it does appear even more counter-intuitive, the mixing of all light colors produces the color we ‘see’ as white (but has NO color? – white… or does it?). Read the rest of this entry »


Making Optics Demos Easier


Marty Sagendorfby:  Martin Sagendorf

We’ve all likely encountered the time-consuming effort required to set up an optics demo; all the necessary components are on hand, but they don’t easily work together.  The difficulty is obvious: the various components are either ‘loose’ or mounted at differing heights.  Thus: wasted and frustrating time ‘shimming’ with books and pads to match the heights of the components.

The solution is simple: choose a height (above bench top) and mount every optical component at the same (optical centerline) height.  But, how does one choose a height?  Simple: first, determine the optical component with the highest centerline then second, build supports for all the other components – matching this centerline height.

I began with a 100 Watt clear light bulb mounted upon a wooden base – the center of the filament was 4-3/4” above the bench top.  I then ensured that everything else I had, or planned to incorporate in demos, could be centered at this height.

The supports shown in the following illustrations are of ¾” pine – either screwed or glued together.  Where required, various combinations of rubber feet and jackscrews provide support and positioning capability.  When applicable, stacks of steel washers are incorporated to add stability. Read the rest of this entry »