The Mysteries of Light

1. Light as a Photon

In the seventeenth century, Sir Isaac Newton championed the theory that light consisted of tiny particles called corpuscles. Then in 1905, Albert Einstein proposed the existence of discreet energy packets during light transmission.

Heinrich Rudolf Hertz. Photo by Robert Krewaldt, Public domain, via Wikimedia Commons

In 1905, Albert Einstern explained that  Light is a beam of particles called photons. The photons of a light beam have a characteristic energy, called photon energy. When that beam is directed at a metal, the photons collide with the atoms. When an electron within the metal absorbs the energy of a photon sufficiently to break free, it will be ejected, producing the photoelectric effect. Hence, the photoelectric effect is evident that light can assume the characteristics of particles.

What we have provided above are just some of the scientists that discovered that light can assume the characteristic of a particle. There are in fact many more Scientists not mentioned here, e.g. Max Planck who derive the concept of quanta and Einstein extended Planck’s concept to arrive at this photographic effect theory. 

Throughout the centuries, many scientists have been in search of the mysteries of Light. In the next section, we shall examine how Light was discovered to assume the characteristics of Electromagnet Wave.

2. Light as an EM Wave

Electromagnetic waves (also known as EM Waves) are formed when an electric field comes in contact with a magnetic field. Hence we call these waves ‘electromagnetic’ waves. Light is one of the many electromagnetic waves in the universe. In fact, light is the only wave visible to our eyes. All other waves such as x-rays, gamma rays, radio waves and infrared light are invisible to our eyes. The entire distribution of electromagnetic waves is called the Electromagnetic Spectrum.

Illustration of Electromagnetic Spectrum (image from NASA, available at Wikipedia Commons.)

Light dispersion animation by Lucas Vieira, Public domain, via Wikimedia Commons

Who discovered the Electromagnetic Spectrum?

Infrared Red Light

In the year 1800, Sir William Herschel was exploring how much heat was contained in the different colors of light. To his surprised, he found that the thermometer that was  out of the light had the highest temperature. As a result, he discovered infrared light.

Ultraviolet light

A year later, Johann Wilhelm Ritter , inspired by Sir William Herschel,  discovered ultraviolet light.

Light as EM Waves

In 1845, Michael Faraday  found that the plane of vibration of a beam of linearly polarized light incident on a piece of glass rotated when a magnetic field was applied in the direction of propagation of the beam. This was one of the first indications that electromagnetism and light were related. In May 1846, Faraday published the article Thoughts on Ray Vibrations, in which he speculated that light could be a vibration of the electric and magnetic lines of force.

In the 1860s, the Scottish physicist James Clerk Maxwell, unified the fields of electricity, magnetism, and optics. In his formulation of electromagnetism, Maxwell described light as a propagating wave of electric and magnetic fields. He predicted the existence of electromagnetic radiation: coupled electric and magnetic fields traveling as waves at a speed equal to the known speed of light.

Radio Waves

In 1887 Heinrich Hertz demonstrated the existence of radio waves in his laboratory.

X-Rays

German scientist, Wilhelm Conrad Röntgen, discovered x-Ray in 1895 by accident and he took an X-ray photograph of his wife’s hand, revealed her wedding ring and her bone. It wasn’t until 1912 that scientists were able to conclude x-Ray is another form of light.

Gamma Rays

Gamma-rays were first observed in 1900 by Paul Villard when he was investigating radiation from radium. In 1914, when Ernest Rutherford observed that they could be reflected off the layers of a crystal, it was clear that they another form of light.