What Is the Formula for Energy? Who Discovered the Particle Theory? How to Convert Nanometers to Joules. What Is the 5th Dimension? Simple Chemical Reactions in Fireworks. How to Calculate the First Ionization Energy of the Kiger Dec 10, If you're a fan of the Netflix series " Stranger Things ," you've seen the climatic season three scene, in which Dustin tries to cajole his brainy long-distance girlfriend Suzie over a ham radio connection into telling him the precise value of something called Planck's constant, which also happens to be the code to open a safe that contains the keys needed to close the gate to a malevolent alternative universe.
But before Suzie will recite the magic number, she exacts a high price: Dustin has to sing the theme song to the movie "The NeverEnding Story. The constant — devised in by a German physicist named Max Planck , who would win the Nobel Prize for his work — is a crucial part of quantum mechanics , the branch of physics which deals with the tiny particles that make up matter and the forces involved in their interactions.
From computer chips and solar panels to lasers, "it's the physics that explains how everything works. Planck and other physicists in the late s and early s were trying to understand the difference between classical mechanics — that is, the motion of bodies in the observable world around us, described by Sir Isaac Newton in the late s — and an invisible world of the ultrasmall, where energy behaves in some ways like a wave and in some ways like a particle, also known as a photon.
As an explanation, he cites the example of a familiar harmonic oscillator , a child on a swing set. Hence, the child can swing at any continuous range of energies from zero up to a certain point.
But when you get down to the level of quantum mechanics, things behave differently. Only a certain amount of energy is allowed. Planck's constant defines the amount of energy that a photon can carry, according to the frequency of the wave in which it travels.
Electromagnetic radiation and elementary particles "display intrinsically both particle and wave properties," explains Fred Cooper , an external professor at the Santa Fe Institute , an independent research center in New Mexico, by email. You may think you are familiar with units, but I think your question suggests you should try to become even more familiar.
I would recommend you first return to some very simple examples of units, and then gradually generalize until you have really 'got' it, where I mean understood it fully, to the point where your intuition and instincts align with your reasoning faculty.
So a simple example would be buying bananas. Suppose, for the sake of argument, that the supermarket sells bananas in groups of 5. It is arranged that every bunch of bananas has 5 bananas. Then we can measure the number of items of fruit either in bananas or in bunches. Your question about Planck's constant is like someone giving you a box of fruit and asking for calculations involving the contents of the box, and you are asking "should I use bananas or bunches when doing calculations and reporting results?
But since energy is less familiar than items of fruit, I'll write a bit more in order to work up to the example of electron-volts. We might go next to other familiar examples such as distance which can be measured in metres, miles, inches, millimetres etc. I am sure all this is reasonably familiar. From these one can construct units of velocitynot just the familiar metres per second and miles per hour, but also all other combinations such as inches per year and things like that. The point is that although the conversion factors are often real numbers rather than simple ratios of integers, all this involves fundamentally the same idea as my original example of bananas and bunches.
Now we come to electron-volts. The first thing is to be clear that the electron-volt is a unit of energy. It is not a charge or a voltage or a time or a banana but an energy. Then by using the definition the first line below one can begin to work with it:. When in doubt always use SI units or SI derived units. Then one can plug the values in the formula and gets the correct result in SI units or the SI derived unit corresponding to the physical quantity. The other form with eVs is there for convenience and can be used if one tracks the units.
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