The Camera Obscura

artist inside camera obscura
Camera Obscura at the time of the Renaissance

"Who would believe that so small a space could contain the image of all the universe? O mighty process! What talent can avail to penetrate a nature such as these? What tongue will it be that can unfold so great a wonder? Verily, none! This it is that guides the human discourse to the considering of divine things. Here the figures, here the colors, here all the images of every part of the universe are contracted to a point. O what a point is so marvelous!"

--Leonardo Da Vinci

Leonardo - discussion of the camera obscura & his observation of the spectrum through a prism
(Confiding his discovery only to his notebooks, for fear that he'd be persecuted as a witch)

Camera Obscura at National Geographic | History of Camera Obscura at Obscura Journal

Pinhole Cameras at Kodak | Pinhole Cameras at Alternative Photography

Leonardo da Vinci at: The Telegraph | Museum of Science, Boston


c. 1677 , Isaac Newton proposed the
Corpuscular Theory of Light:

Newton's theory

Light: Particle or a Wave? at Olympus

Newton's Corpuscular ("Particle") Theory at Canon



Wave Theory of Light, 1677

Christiaan Huygens - comparison of light to sound waves
("longitudinal vibrations")

Christiaan Huygens Wave Theory at Space and Motion

"Around every particle there has to arise a spherical wave,
which this particle is the center."

"particles" in waves
Science Photo Library/
Photo Researchers, Inc.

1801 - Thomas Young devises the "double-slit experiment"
to demonstrate the interference of light waves, validating

Thomas Young's Double Slit Experiment at Florida State University

Wave Theory in action


c. 1555 - Georgius Agricola
"The Father of Mineralogy", Agricola
Believed chemical makeup can be
determined by the color of a flame

Georgius Agricola at
University of California, Berkeley



Agricola's theory was proven with the development of the first spectroscope by Dr. Henry Draper in 1872,
made from a cigar box, prism and telescope parts.


This device reveals the "line spectrum"; for example, potassium was represented by a single red line, etc.

Line Spectrum identifications of certain elements & their relationship to the visible spectrum:

line spectrum


Pierre Janssen and the Solar Eclipse of 1868
The spectrometer (spectroscope) used in solar eclipse -
is discovered as a single yellow line.

19ht century illustration of sprecroscope
early spectroscope


Janssen at Wikipedia


1900 - Max Planck definitively proves the particle theory of light while studying heat and the continuous exchange of energy using black body radiation.
He recognized light is not continuous but composed of particles he calls "quanta".

Planck, then Einstein, developed the Quanta theory of light

Albert Einstein at Hyper History

Max Planck at Physics of the Universe

Planck's Quantum Theory at



1913 - Neils Bohr discovers that atoms absorb light rays that are energy specific to their makeup.

Demonstration drawing of an electron emitting energy as it drops to its previous lower orbit, after having been stimulated to higher orbit by a photon:

atom absorbing and releasing energy
The higher orbit of the electron represents a higher energy level

Black Body Radiation and The Quantum Jump at Weber State University

Bohr's Atomic Model at Purdue University and University of Oregon



Heat and Light

Discussion of the dual nature of light - from an invisible ray to materialization as a "tiny projectile" upon contact with matter.

Example of dual nature -
In experiments, when positrons and electrons of equal size met, they did not rebound, as expected,
but disappeared in a release of a very short wavelength of energy that was equal to the energy level of both. This process has also been reversed.

Concept of "heat" discussed -
molecular movement -

kinetic energy as explanation of heat.

Description of metal in heated, glowing,
melting and boiling stages to illustrate the relationship between movement and heat/light.

Concept of "stray atom" during boiling stage leads to brief discussion on particle speed and mass.

"Conductors of heat" - iron & wood contrasted

Description of gas compression and expansion in refrigerators to help convey notion of molecular activity producing heat or "less heat" (cold).

Concept of "molecular repose" (absolute zero)

Brief description of superconductivity - property of elements to better conduct electricity at super cooled temperatures.