Light and Electrons!

Electrons are fundamental particles and play an important role in most of the physical phenomena spanning from static electricity to complex chemical and nuclear reactions. Although the existence of this negatively charged entity was theorized in the first half of the 18th century (1)(2), it was discovered by Sir J.J.Thompson in the year 1897 in the form of cathode rays.(3) This discovery is considered to be a highly important for the development of science and technology. The flow of these tiny particles is what drives the sophisticated electronic and electrical equipment, which have become an integral part of life.

Aurorae are mostly caused by energetic electrons precipitating into the atmosphere.

Aurorae are mostly caused by energetic electrons precipitating into the atmosphere. Credit: Samuel Blanc / Wikimedia Commons

The theory of electrostatics, electrodynamics and electromagnetism was developed due to the combined efforts of many eminent scientists over the last century. We were able to detect electronic transitions and identify the spectral lines corresponding to those transitions in various systems. With the help of quantum mechanics (4), we gained a better understanding about various atomic and molecular phenomena caused by the movement of electrons. This eventually led to the development of the first LASER. Since then we have seen how largely optics and photonics have contributed to science.

We now talk about photonic integrated circuits, optical computers, and the future of photonics.(5) But can we really eliminate electronic devices? First of all, light emission and most of electromagnetic radiation is mostly because of electronic transitions. Other effects like Bremsstrahlung, Beta-decay, thermionic emission, field emission et cetera are also responsible for emission of electromagnetic radiation. Gamma-rays can be produced when there is an electron-positron annihilation reaction. (6)

Even when we try to quantify these events, we use detectors which convert the electromagnetic energy into an electronic signal. Usually we make use of avalanche photodiodes, photodetectors, charged coupled device (CCD), complimentary metal-oxide semiconductor (CMOS) cameras et cetera. (7)

We still do not have the technology to measure or quantify light with light! It may sound absurd but the underlying point is the intricate relation between light which is a form of electromagnetic radiation and electrons!

Someday we may have devices based solely on light, running on photons but the day is nowhere near. Our current systems still make heavy use of electronic detectors, emitters and other processing equipment. Although there is a strong analogy between optical and electronic systems like a photonic crystal and semiconductor, we are far away from utilizing the complete potential of optical systems.

More Information

1 – Farrar, W.V. (1969). “Richard Laming and the Coal-Gas Industry, with His Views on the Structure of Matter”. Annals of Science 25 (3): 243–254. doi:10.1080/00033796900200141.

2 – Buchwald, J.Z.; Warwick, A. (2001). “Histories of the Electron: The Birth of Microphysics” MIT Press. pp. 195–203. ISBN 0-262-52424-4.

3 – Thomson, J.J. (1897). “Cathode Rays”. Philosophical Magazine 44 (269): 293.doi:10.1080/14786449708621070

4 – Schrödinger, E. (1926). “Quantisierung als Eigenwertproblem”. Annalen der Physik (in German) 385 (13): 437–490  doi:10.1002/andp.19263851302

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phatakAbhijeet Phatak is a final year undergraduate student at the Department of Ceramic Engineering, Indian Institute of Technology (Banaras Hindu University), Varanasi, India ( His research interests include optics, photonics, materials science, ceramic materials, nanotechnology, semiconductors, energy, metamaterials, quantum effects, computational physics and other sciences. Pursuing further research, he wishes to do something that will have a great and positive impact on the society.


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