a publication of the International School of Gemology 18 September 2013

Measuring the Energy of Light

During last night's ISG Journey Thru Gemology classroom presentation we reviewed how gemstones produce their individual color(s) by absorbing certain colors of light and transmitting other colors. This is based on the different colors of light having different energy levels, and how a gemstone utilizes this energy. To demonstrate the concept of different energy levels of light colors the ISG developed a demonstration that allows students to actually see the different energy available at different light wavelengths. Based on the discussions among our group that could not attend, we have been asked to show this demonstration here in our newsletter today. So for all of you who could not attend we bring you a simple demonstration of Measuring the Energy of Light.

Purpose of the Demonstration

The purpose of this demonstration is to show that different wavelengths (or colors) of light have different energy levels. That is why gemstones can take the same ambient white light containing all colors, and absorb some while transmitting others and produce a variety of colors based on the characteristics of the gemstone.

Method of Demonstration

For this demonstration we measured the thermal temperature of light from the sun using a Plexiglas™ prism, Vicks™ baby thermometer and Canon A520 camera. As you can see below, the prism was placed on a table on a back yard porch with the prism located as to transmit the solar spectrum on a shaded location of the floor of the porch.

Using this set-up we next placed our thermometer on the floor and in the spectrum light of the sun which was produced by our prism. The ambient temperature in the shady portion of the porch on this day was 82°F. Here are our results...


When the thermometer was placed in the blue/violet portion of the spectrum, the temperature initially went up to 90.8°F and stabilized at 90.9°F where it maintained for several minutes.
After allowing the thermometer to reset to the ambient shade temperature of the back porch, we then placed the testing portion in the far red end of the solar spectrum being projected on the floor. As you can see below, the initial response was to record a temperature of 91.4°F and finally stabilized for several minutes at a temperature of 91.8°F, almost a full degree hotter in the red end of the spectrum than the blue end.


While we realize this is just a back yard test of limited formal scientific value, we believe that it does serve to demonstrate that different colors of light have different levels of energy. In this case we have a thermal energy variable between the red and blue ends of the spectrum. If we take this concept of different energies in different colors of light, we can better understand a gemstone's ability to utilize the different colors of light to create different gemstone colors. The full explanation of the selective absorption of energy and how it produces colors was covered in last night's Journey Thru Gemology and in the ISG Colored Gemstones course notes.
At the ISG we work very hard to not only make the study of gemology fun and affordable, we also work very hard to make the more complicated concepts of gemology easier to understand for others like us who are just plain folks. We hope this demonstration has accomplished that goal for others out there who, like ourselves, love gemstones and want to learn more about them based on a grass roots level of knowledge and study.

If you would like to join us in the ISG Journey Thru Gemology on Tuesday nights, we invite you to become a part of the ISG Community by joining us for the study of gemology. Our Introduction to Gemology course is only $95.00 and will serve as your portal into the amazing world of gemstones and all of the wonderful people who are already a part of the ISG Community. Click the ISG Journey Thru Gemology ticket at left to visit the ISG and learn more.

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