Light is everywhere. It is there when we wake up and the Sun is blinding our eyes. It is there when night falls and we flick switches and press buttons to turn on our lightbulbs. It helps us see the people around us.
Pythagoras, who you might know for the Pythagorean Theorem (a squared plus b squared equals c squared), guessed that light rays come from the eyes and then strike an object. Epicurus, an Ancient Greek philosopher like Pythagoras, said the opposite: light rays come from the objects and strike the eye.
In 1690, Dutch mathematician-astronomer Christiaan Huygens described the undulatory theory, which was about an invisible medium substance that carries waves (e.g. sound waves) that fill all the empty space between objects (like air). He thought that light occurs when a luminous object (something that emits light by itself, for example, the Sun) emits a bunch of waves/vibrations in the medium.
In 1704, Newton described light as particles. He saw that light travels in a straight line and bounces off of a mirror kind of the same way as a ball bouncing off of a wall would.
Reflection is when a light ray strikes a smooth surface and bounces straight back. In our world of imperfect surfaces, mirrors are the closest thing to a perfectly smooth surface. The law of reflection says that the angle at which the ray of light is striking the surface is equal to the angle at which it bounces back from the surface. In our world, when light strikes a surface that is not smooth, the angles are a bit uneven, which is called scattering.
The Arab scientist Ibn al-Haytham (965-1039 AD) discovered the law of refraction. Refraction is when light passes one medium to another medium. For example, if you put a pencil in a glass of water, you can see that the part of the pencil that is in the water looks different from the pencil that is hanging in the air.
In 1801, the English physicist and physician, Thomas Young did the double-slit experiment. The experiment consists of a light source, a pinhole, a thin card that has two holes cut next to each other, and a screen. Young used the light source to have light pass through a pinhole and then strike the card that had the two holes.
He thought that if light were truly made up of particles, it would be blocked by the card and wouldn’t travel to the screen so the screen would showcase two “holes.” Instead, he saw a barcode-like pattern of light and dark bands on the screen.
He proposed a new theory: light is actually made up of waves. This helped scientists come up with explanations for new things that had been a mystery. This new theory of light waves still obeyed the rules of reflection and refraction. James Maxwell, a Scottish physicist, then came up with the theory of electromagnetism in the 1860s. He saw light as having electric and magnetic fields.
Albert Einstein and his first wife, Mileva Maric, studied the photoelectric effect. They shined ultraviolet light on a metal surface and were able to detect electrons being emitted from the surface. Einstein and Maric concluded that light could be thought of as having small lumps called photons. When photons strike a metal surface, they excite the electrons and the electrons move along the metal. They also used the speed of light (299,792,458 m/s) for new concepts.
Atoms are the smallest building blocks of matter. They are made up of protons, neutrons, and electrons. Positively charged protons and the no charge neutrons reside in the nucleus of the atom. Electrons have a negative charge and orbit around the nucleus. Electrons are technically “stuck” to protons but the reason they aren’t that close is that electrons have a certain wavelength that gives them certain properties. The wavelengths can’t change much without changing the electron itself. And electrons, like photons, have both properties of waves and particles (which is why there was a theory discussed earlier that light was made up of particles).
Physicists have come to accept the wave-particle duality property of light. Even in the dark, our eyes are able to detect a few photons. Because of photons, we are able to see the world.
Vaageesha Das is a sophomore at Morgantown High School. Today’s information comes from: Craig Freudenrich, P.D. (2020, January 27). How Light Works. Retrieved from https://science.how
stuffworks.com/light.htm; Dubey, R. (2017, November 10). Why are electrons not attracted to protons? Retrieved from https://www.
quora.com/Why-are-electrons-not-attracted-to-protons; Parida, S. (2017, July 27). What is the formula for finding the number of shells of a given atomic number? Retrieved from https://www.
quora.com/What-is-the-formula-for-finding-the-number-of-shells-of-a-given-atomic-number; Speed of light. (2020, April 12). Retrieved from https://en.wikipedia.org
/wiki/Speed_of_light
