The photoelectric effect details how electrons can be ionized by photons based on the wavelength of If a quantum of light comes in with enough energy, it can interact with and ionize an electron, kicking it out of the material and leading to a detectable signal.
We can illustrate why by examining the photon: the quantum of energy associated with light. Light comes in a variety of energies, from the ultra-high energy gamma rays down through the ultra-low energy radio waves. But light's energy is closely related to its wavelength: the higher the energy, the shorter the wavelength. The lowest energy radio waves we know about are many meters or even kilometers long, with their oscillating electric and magnetic fields being useful in causing the electrons inside antennae to move back-and-forth, creating a signal that we can use and extract.
Gamma rays, on the other hand, can be so high in energy that it takes tens of thousands of wavelengths to fit across even a single proton.
If the size of your particle is larger than your wavelength of light, the light can measure its size. Double slit experiments performed with light produce interference patterns, as they do for any wave The properties of different light colors is understood to be due to the differing wavelengths of monochromatic light of various colors.
Redder colors have longer wavelengths, lower energies, and more spread-out interference patterns; bluer colors have shorter wavelengths, higher energies, and more closely bunched maxima and minima in the interference pattern. But if your particle is smaller than the light's wavelength, the light won't be able to interact with that particle very well, and will behave like a wave.
This is why low-energy photons, like visible light photons, will create an interference pattern when they're passed through a double slit. So long as the slits are large enough that the light's wavelength can get through them, you'll get an interference pattern on the other side, demonstrating this wave-like behavior. This is true even if you send the photons through one-at-a-time, indicating that this wave-like nature isn't occurring between different photons, but that each individual photon is interfering with itself somehow.
This remains true even if you replace the photons with electrons, as even massive particles can act like waves under low-energy conditions. Even low-energy electrons sent one-at-a-time through a double slit can add up to produce that interference pattern, demonstrating their wave-like behavior.
Most of us view atoms as collections of atomic nuclei orbited by individual electrons. While this When we picture an atom, most of us instinctively revert to that first model we all learned: of a point-like electron orbiting a small, dense nucleus.
This "planetary model" of the atom first came about due to Rutherford, and was later refined by Niels Bohr and Arnold Sommerfeld, who recognized the need for discrete energy levels.
But for the better part of the past century, we've recognized that these models are too particle-like to describe what's actually occurring. Electrons do occupy discrete energy levels, but that doesn't translate into planetary-like orbits. Instead, the electrons in an atom behave more like a cloud: a diffuse fog that's spread out over a particular volume of space.
When you see illustrations of atomic orbitals, they're basically showing you the wave-like shape of the individual electrons. The each s orbital red , each of the p orbitals yellow , the d orbitals blue and the f orbitals If you were to send a high-energy photon or particle in there to interact with an electron, sure, you could pin down its position precisely.
But — and here's where quantum mechanics trips most of us up — the act of sending that high-energy particle in there fundamentally changes what's going on inside the atom itself. It causes the electron to behave like a particle, at least for the moment of that one interaction, instead of like a wave. But until such an interaction occurs, the electron has been acting like a wave all along. Learn more. If everything is made up of atoms why doesn't every thing look the same?
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Carbon is a solid at room temperature, oxygen is a gas, Carbon dioxide is also a gas. And there are quite literally an infinite number of possible molecules! The molecular situation is even more complex than I described. It's not just the composition of the molecule but also the structure. Show 3 more comments. Helium is the only one found on its own. I have corrected my answer to reflect your observation. Hobbes Hobbes 2 2 silver badges 3 3 bronze badges.
Although, I take it that unlike pets we can assume that some of these elements don't look like the people they are named after.. Berkelium, californium, and einsteinium have also all been synthesized in macroscopic quantities, so there are probably photographs of them yes, silvery or grey metals floating around.
Only that to a good approximation, the properties of matter that humans experience in everyday life i. BioPhysicist Nuclei are made of protons and neutrons. Protons and neutrons are made of quarks and gluons.
It all started with the big bang some 14 billion years ago. Not that this is relevant to the question at hand. Featured on Meta. Now live: A fully responsive profile. Linked 0. But the proportions of each element in the various combinations always reduced to very small numbers. If matter was infinitely divisible, with no smallest possible bit, then any proportion ought to be allowed. Instead, he found that a certain amount of one element might combine with an equal amount of another element.
Or with twice or three times the other element. Dalton found only simple proportions, everywhere, in all cases. If matter was ultimately indivisible, if it was made of atoms, then only simple proportions and ratios would be allowed when combining elements.
A hundred years later, this "atomic" theory of matter didn't seem completely nonsensical. One of the most challenging things about it, however, was that if atoms really existed, they were way, way too small to see. How could you prove the existence of something you couldn't directly observe? One clue to the existence of atoms came from the newly established studies of thermodynamics. In order to understand how heat engines worked — along with all the attendant concepts like temperature, pressure and entropy — physicists realized that they could view gases and fluids as if they were composed of a nearly numberless quantity of tiny, even microscopic, particles.
For example, "temperature" really measures the average motion of all those gas particles hitting your thermometer, transferring their energy to it. This was pretty compelling, and Albert Einstein was a big fan of these kinds of physics.
Just like all the other physics that he became a fan of, Einstein revolutionized them. He was interested, in particular, by the problem of Brownian motion, first described way back in by Robert Brown hence the name.
If you drop a large grain inside a fluid, the object tends to wiggle and jump around completely on its own. And after a few carefully executed experiments, Brown realized that this has nothing to do with air or fluid currents. Brownian motion was just one of those random unexplained facts of life, but Einstein saw in that a clue.
By treating the fluid as something composed of atoms, he was able to derive a formula for how much the innumerable collisions from the fluid particles would nudge that grain around.
And by putting this connection on solid mathematical ground, he was able to provide a pathway for going from something you can see how much the grain moves around in a given amount of time to something you can't the mass of the particles of the fluid. And just when people were getting comfortable with the size of these minuscule morsels of matter, thinking that these had to be the smallest things possible, someone came along to complicate it.
Operating in parallel with Einstein was a wonderfully gifted experimentalist by the name of J. In the late s, he become enraptured with ghostly beams of light known as cathode rays.
If you stick a couple electrodes inside a glass tube, suck all the air out of the tube, then crank up the voltage on the electrodes, you get an effervescent glow that appears to emanate from one of the electrodes, the cathode, to be exact. Hence, cathode rays.
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