Early observations of Fluorescence from wood of the narra tree in the 1560's.
Fluorescence accidentally isolated in 1602 by an alchemist who was experimentally baking substances in the search for gold,
which, in this case, glowed in the dark, even after cooling.

Hennig Brand depicted in painting
painting by Joseph Wright, 1795

In 1669 Hennig Brand, also an alchemist, this time searching for gold in evaporated urine, discovered phosphorus.
Ultraviolet light is absorbed by substances such as these and the energy is slowly released as visible light, over a period of time,
due to substances known as "impurity elements".

Chemiluminescence at Chemistry Explained

Hennig Brand and Phosphorus at Chemistry Explained



luminous fish

Brief discussion of luminous creatures -
tiny fish, fireflies, etc. -

How they are "light efficient" ("cold light");
How this is possible due to a special enzyme.


Bioluminescence at Smithsonian Institute


Self-illuminating creatures &
experiments in Industry
with "bacteria lights" in areas where
electricity can be dangerous (mines, etc.).


Glow In The Dark Bacterial Lights at New Scientist

Glow in the Dark Microbe Lamp

microbe lamp
© Glowee



Molecules of Rhodopsin detect light
- detail of the Retina

detail of retina

Mention made again of "opsins" from the retina -
this time to state that the "pain" that is felt when eyes are "adjusting" to the light after exiting a dark room
(such as leaving a movie theater & entering bright sunlight)
is due to the rapid production of these light sensitive proteins by the eye due to the fact they were used less in the dark, therefore the eye had decreased manufacture.

opsins in the role of translating sense perception into electrical signal for visual cortex:
Scotopic (night) and Photopic (day) Vision.

Rhodopsin and the Eye at University of Bristol


Description of effects in the atmosphere by ultra violet radiation:
the refraction of light waves between denser & less dense (cooler & warmer)
masses of air produces the "twinkling" effect of stars and the
shimmering "mirage" effect in the desert or at the
end of a long road or sidewalk on a hot summer day.

Wave Behaviors at NASA

Light at Stony Brook University

The Physics of Waves at Massachusetts Institute of Technology

Atmospheric Refraction

Refraction of Light in Atmosphere


heat energy produced by tungsten bulb

This chart demonstrates how most energy
produced by Filament Bulbs is heat energy,
not visible light

Contrast of Filament Light Bulb with Fluorescent Bulb

Tungsten metal is the preferred filament due to its high melting temperature, luminosity & durability.

Filament bulbs are bright, but produce more heat than light.

Fluorescent bulbs produce so-called "cold light",
in other words more light than heat. Unlike the heating of the filament,
the gas in the tube is stimulated by electricity,
which is energized to radiance.

Filament Light Bulb vs. Fluorescent Bulb at Diffen


Description of Geissler Tube

(Heinrich Geißler) 1857

Discovery of greenish lines emanating from the electric current
passing through the gas.
Thought at first to be a new ray.

Geissler Tubes at The Cathode Ray Tube Site

Crookes and Geissler Tubes at Spark Museum

Geissler Tube at Wikipedia

Heinrich Geissler at:
The Cathode Ray Tube Site | Encyclopedia.com
| Wikiwand

Geissler Tube Rotator 4


Scientists couldn't get the rays to pass through the glass in order to better study them, but by 1891 it was discovered that the rays would pass through ultra thin aluminum, proving their subatomic size. Several scientists worked independently over about 30 years on these studies, in some cases modifying the tube:

Note the development of the Fluorescent Screen
Braun tube


The "Braun Tube"
after Karl Ferdinand Braun

Ferdinand Braun photo

Ferdinand Braun at NobelPrize.org

The Ferdinand Braun Institute


© 2000 Benjamin/Cummings; imprint Addison Wesley Longman, Inc.


"Cathode Ray Beams" are now known to be "Free electrons". (Thomson first called them "electric atoms", later renamed electrons).
He discovered he could direct this beam by way of magnetic fields. Eventually the rays could be focused by passing them through a magnetized coil or aperture (Hans Busch & "electron optics", which led to development of the electron microscope - providing magnification of 300,000 times, far more was learned about viruses and other studies).

Hans Busch at WOW.com

Microscopy at John Innes Centre

Ernst Ruska and the First Electron Microscope at Florida State University


Such control of electrons led to the development of the television tube with its "electron gun", itself a cathode (electrode with negative charge). The beam is directed to a fluorescent screen, but first must pass through a thin metal coating (deposited by vaporization) to increase brightness.


electron emitter in TV

Electron Gun at Wikipedia


Infrared microscopy, which must be specially photographed because the rays are outside the visible spectrum, nevertheless provides better magnification (5000x) than visible light (3000x) because the rays are shorter. Objects smaller than half the wavelength of a violet lightwave cannot be "resolved" by ordinary light.

Far superior even to infrared microscopy in magnification because of the tiny size of the electron, electron microscopy nevertheless produces a silhouette-like image by "refocusing" the electrons after they pass around the object. (This effect is similar to the passing of pollen through a screen by the wind and having an impression of the screen design on the door behind the screen).

Optical rules of "refraction" do not apply.


mid-century infra-red microscope

Infrared Microscopy at Wikipedia


Infrared Photography

Infrared Landscape photo
Robert Williams Wood, 1910 - Infrared Photo Pioneer

Robert Williams Wood at National Academies Press

Introduction to Infrared Photography at Photography Life

History of Infrared Photography at LifePixel

Night Vision

Developed by the Germans in WWII:

The Zielgerät 1229 at Wikipedia
Night Vision History at Armasight
German Infrared Night-Vision Devices at Achtung Panzer


Description of "infrared vision"

Infrared light beams bounce off object like ordinary light, but is invisible to human eyes.
This light is reflected back onto a screen that dislodges electrons because of its contact with the infrared radiation.
These dislodged electrons are magnetically focused onto another screen, which absorbs this energy and "fluoresces" visible light.


Aurora Borealis - The "Northern Lights" at earth's poles

Aurora Borealis

Solar flare activity releases "prominences" as long as 600,000 miles long - which send electrons to earth within about two days. This produces an
"electric storm" and also lights up the northern sky.

The electrons are drawn to the magnetic poles, where they stimulate the nitrogen & oxygen atoms to fluorescence.

A laboratory test of suspending a magnetized iron sphere & directing a electron beam at it demonstrated the electrons diverting to the poles and producing a blueish-white glow.

This magnetic phenomena also produces the "electron free zone"
at the equator.

Northern Lights at Northern Lights Centre

Aurora Borealis at EarthSky

Solar Wind at Wikipedia


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