Wednesday, September 9, 2009

The amount of electrons emitted after exposure to electromagnetic radiation was proportional to the intensity of the radiation?

Hi All

Here is another interesting reply from Dr. Andrew Goldsworthy. 

I sent him a question about the work of Albert Einstein, on the issue of electro magnetic radiation.  The article and my question are located at the lower part of this page.

His reply helps to explain in simple terms, why electro magnetic radiation is harming people, animals, birds and the environment.

Martin Weatherall



Sent: Wednesday, September 09, 2009 10:24 AM

Subject: Re: The amount of electrons emitted after exposure to electromagnetic radiation was proportional to the intensity of the radiation

Hi Martin,

What the article is saying that electromagnetic radiation comes in small packets called photons or quanta, the energy of which is proportional to its frequency. It is relevant to us because a molecule can only absorb one photon at a time and the effect it can have on that molecule is limited by the energy of that photon.

This notion was pounced upon by the cell phone industry and others, who asserted that because the energy of photons of non-ionizing radiation had insufficient energy to break chemical bonds, it must be without biological effects.

This is of course not true. It can still cause structural changes in molecules. For example the photons of non-ionizing light cause structural changes in chlorophyll, the energy of which are used for photosynthesis. Similarly, structural changes in the visual pigments of the eye allow us to detect light and see.

The still lower photon energies of radio waves can still move free electrons and ions, which is why they generate electric currents in the antennas of radio equipment and in living tissues. It is these currents, and the voltages they generate across cell membranes, that appear to do much of the damage to living cells and tissues.

At least some of this damage is caused by the release of calcium ions from cell membranes (or more strictly, their replacement by monovalent ions), which damages them and makes them more inclined to leak. Very little energy is necessary for this since the ions concerned have only to be moved by molecular dimensions and the effect is just to change the natural chemical equilibrium that already exists between calcium and monovalent ions bound to the membrane.  This is a continuous process and there is no threshold value below which there is no effect.

However, the resulting damage is out of all proportion to the energy of the radiation. Enzymes released from damaged lysosomes can digest the rest of the cell, and free radicals released from damaged mitochondria can destroy other molecules, including DNA. Non-ionizing radiation should therefore be treated with as much caution as ionizing radiation.

Best wishes


(Dr Andrew Goldsworthy)


On Wed, 9/9/09, Martin Weatherall <> wrote:

Hi Andrew

I just read this article an wondered if the section that I highlighted is of any special interest?



Nobel Prize Winners: Albert Einstein

Lia Cardarelli

The Prize:

The 1921 Nobel Prize in Physics to Albert Einstein "for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect."

The Science:

Known as "The Miracle Year," 1905 saw Einstein publish four papers that changed the face of modern physics. In large part to celebrate the hundredth anniversary of these publications, 2005 was declared World Year of Physics. Though each paper Einstein published in the Annalen der Physik—on the photoelectric effect, Brownian motion, special relativity, and the energy-matter equivalence (the famous E=mc2)—was significant, the Nobel was awarded to him specifically for work on the photoelectric effect.

Many physicists in the late 19th and early 20th century were studying the photoelectric effect, which describes the release of electrons from surfaces that are exposed to electromagnetic radiation, the spectrum of wave frequencies that spans radio waves to visible light to X-rays and gamma rays. The effect, in a nutshell, is when a surface absorbs light and it releases electrons.

Early work by Bequerel, Hertz, and Thomson led to the understanding that the amount of electrons emitted after exposure to electromagnetic radiation was proportional to the intensity of the radiation.

Then, in 1902, Philipp Eduard Anton von Lenard threw the physics equivalent of a curveball. That year Lenard published a paper describing how altering light frequency (meaning the length of the wave, not the duration of exposure) changes the photoelectric effect. When light below a certain frequency shines on a piece of metal, it fails to release electrons, even if applied with very high intensity light. High-frequency light, such as ultra-violet light, releases electrons with higher energy than the electrons emitted by lower-frequency light.

Lenard's findings were puzzling because they could not be explained by the properties of light as they were then understood. Most physicists of the day held the opinion that light is an indivisible wave. In the late 19th century Planck (like Newton before him) postulated that instead of being an indivisible wave, energy existed in discrete amounts, which he called quanta.

Planck's findings were able to explain this phenomenon and showed that the energy of these particles could only exist in multiples of what is now known as Planck's constant, h. This means that radiation energy can only be observed in integer "jumps" of h, no in-betweens.

Einstein's 1905 paper brought these two puzzles together, postulating that Planck's quantum theory of radiation could explain the photoelectric effect discrepancy seen by Lenard. He described the energy of each quantum of light as equal to the product of its frequency (its wave-length, or colour) and h (Planck's constant). Light with a higher frequency will therefore direct greater energy at a surface. Therefore, light with a frequency below a certain threshold does not cause a surface to emit electrons, regardless of the light's intensity. At a certain frequency, an incoming light particle has enough energy to dislodge the emitted electron (this is called the "work" function). Increasing the intensity of the light releases more electrons, but only if the frequency of the light is above the threshold. The difference between the energy of the incoming light particle and the energy required to dislodge the electron is passed onto the leaving electron as kinetic energy. Thus, light with a higher frequency is able to cause the emission of electrons with higher kinetic energy.

The Significance:

Although published in a leading journal, Einstein's explanation of the photoelectric effect was generally unaccepted in the physics community. Neils Bohr, another prominent physicist, was (at least initially) very opposed to Einstein's theory, which led to the very public Bohr-Einstein debates over understandings of quantum physics. In his 1922 Nobel acceptance speech (a year after Einstein was awarded the prize), Bohr even claimed that "the hypothesis of light-quanta is not able to throw light on the nature of radiation."

It took 16 years for the science community to award Einstein for his work on the photoelectric effect—evidence of the controversy that surrounded his findings. Einstein went on to show that quantized energy could also explain how materials absorb heat. It took much longer to convince the scientific community that light is particle-like. Even though experimental evidence proved his equation, Einstein's theory of the wave-particle duality of light was not accepted as a physical explanation for the photoelectric effect. His work on general relativity reinforced his quantum theory of light, but few would agree with him.

Work by Millikan in 1916 (for which he won the Nobel in Physics in 1923) experimentally proved Einstein's theory by measuring the kinetic energy of emitted electrons and experimentally calculating Planck's constant, h. In the 1920s, experiments firmly proved the duality in light: it behaves as both wave and particle. This dual nature caused Einstein to remark in 1924 on the new puzzle posed by his own findings: "There are now two theories of light, both indispensable...without any logical connection."