Archive for March, 2007

Happy Birthday Doctor Einstein > Photoelectric Effect

Thursday, March 15th, 2007

Artist's Impression     A simple experiment     Einstein

On Pi Day, 1879 Albert Einstein was born.  In 1921 he won the Nobel Prize in Physics, primarily for his pioneering work (pdf) completed March 17, 1905 explaining the photoelectric effect – a couple of months before he wrote about Special Relativity during his Annus Mirabilis.  Coincidentally, 2 other Nobel Prize winners were born within a month of Einstein: Otto Hahn, the father of nuclear chemistry, and Owen Willans Richardson, who also studied the photoelectric effect and explained the sea of electrons in metals.  In 1905 Einstein wrote:

According to the assumption considered here, when a light ray starting from a point is propagated, the energy is not continuously distributed over an ever increasing volume, but it consists of a finite number of energy quanta, localised in space, which move without being divided and which can be absorbed or emitted only as a whole.

In 7th grade I won a first prize in the Bronx county Science Fair with a project called How Does a Photelectric Cell Convert Light Energy into Electrical Energy.  The setup was a photocell connected in series to a microammeter and a standard light source aka a candle.  I spoke to the particle nature of light, but what I measured was the inverse square law for light.  I had the help of a neighbor, who was a physicist, in designing the experiment. The funny part is I thought my experiment was too simple to be any good.  I envied the nuclear battleship model, and other such elaborate things.  In 7th grade I knew nothing about Einstein’s Nobel Prize, or the elegance of physics.

Inverse Square Law

Today, in what is described as an experimental masterwork, French physicists claim to be able to trap a single photon in an “Einstein box.”

Einstein Box

Incidentally, Einstein got an average performance review in 1905.