E = mc² : Mass-energy equivalance
E=mc^2 is probably the most famous equation in physics but even though most people have heard of it, few know what it actually means. You might have heard people say things like: “Mass is compressed energy” or that energy can be converted into mass. Unfortunately, both statements are wrong and while it is true that this equation greatly impacted the creation of atomic bombs which might make you think this equation means mass holds huge amounts of energy, that is not the actual fundamental idea of this equivalence. This is because, at its core, Einstein’s equation implies a way of understanding mass, not energy.
Explanation: Any particle's mass depends on the distance and arrangement between it's individual "ingredients" because different distances between those parts result in different internal energies that in turn influence the total mass of a particle. The distance between an electron and a proton in a particle can partially determine the mass of a particle because of the internal energies directly changing it's mass.
Incredibly, 2 particles made of identical "ingredients" don't necessarily have the same mass! Why? Because kinetic, potential and other energies have tiny effects on the rest mass of something, unnoticeable in normal life. This means that a ticking watch has more mass than an identical idle watch because the ticking watch has more potential and kinetic energy resulting in greater mass.
The photoelectric effect
The photoelectric effect is the production of electrons or other free carriers(a particle that is free to move carrying an electric charge) when light is shone onto a material. The electrons emitted can be called photoelectrons. But the electrons are only dislodged after the photons (light source) exceed a certain frequency(energy). To make sense of the fact that light can eject electrons even if its intensity is low, Albert Einstein proposed that a beam of light is not a wave propagating through space, but rather a collection of discrete wave packets (photons), each with energy hf;
Unlike in other experiments with light, to undertsand the photoelectric effect it is best to think of light as a particle and not a wave. So what is the photoelectric effect. It's actually pretty simple: Sometimes when light is shone onto a metal, electrons can be released from the metal. Suprisingly, not all frequencies of light can do this. For example blue light, regardless of it's intensisty, can release electrons from the surface of a metal. Red light, if we were to shine to shine it onto a metal would never release electrons from the metal, even if we turned the brightness of the light up, Previous classic theory proposed that the frequency of light shone onto a metal would have a direct im,pact on the electrons would have a direct impact on the electrons released, but in reality a minimum threshold frequency for electron emmsion could be observed. At the time, this was a huge contradiction and a mystery for science.
Einstein proposed that light must come in distinct wave packets called photons, each of which's energy would determine the release of energy. At different light frequencies the individual photons would have different energies, which would determine whether electrons were released and even when the light intensity (brightness) was increased, electrons would not get emmited.
Light at different frequencies shone onto a metal
Einstein had created a new way of understanding light, a new theory to how the world works for which he won the nobel prize of physics in 1921.
Other notable achievements and awards include:
Barnard-Medal, honoris causa, Copley-Medal in 1925, Max-Planck-Medal 1929, Benjamin Franklin Medal 1935, Gold medal of the Royal Astronomical Society 1926, Matteucci-Medal 1921
Albert Einstein was truly an incredible scientist, changing our way of understanding the world we know forever. His way of thinking was unmatched and his research will probably be the fundament of science for a long time to come. He unmistakably is one the most iconic figures in science for good reason.
Thank you for reading! These are my sources:
- Googgle images > Keywords: A. Einstein, Theory of..., twin paradox, nobel prize, e=mc^2...
- Wikipedia articles: Theory of general and special relativity, space-time, photoelectric effect, time dialtion, speed of light...
- Youtube videos: The ones above and: <https://youtu.be/puT36rd9dkQ>