Electron Definition and 999 Threads

What is smallest particle in an electron or a quark?

Hi. I am just starting to self-study particle physics. Came across the following in some notes - Electron and positron annihilate to form a photon with zero momentum. I thought all photons had momentum due to the de Broglie equation ? Also 2 electrons scatter to form a photon with zero energy...

If you know where to look for an electron (e.g. in an atom or an experimental setup) it is quite understandable that, until you know exactly where it is, there is a calculable probability of where it might be. However, if we take the case of an un-associated electron in space, it would seem that...

Kind of the basic question of atomic physics is momentum distribution of single electron of ground state hydrogen atom - especially the power in its high-energy tail (HTMD: high-tail momentum distribution), which should have strong impact especially on various scattering experiments. Fock's 1935...

Guy guy, i just learn a little bit about quantum physics and i know that electrons is not particles. But i don't understand how it move. By the way I am only a secondary school student. If you explain it clearly and easy to understand i'll be very happy. But thank you all for taking time to help me!

Hello mates. I was doing some research about Rydberg atoms, and I came up with this question: what's the energy of an electron in n energy level in an atom which is NOT hydrogen-like, that is, an atom with more than 1 electron? How can we calculate it? What if the electron we are studying is in...

Theres something that bothers me, We claim that electron is a point particle.From that, Can we assume the volume the electron is ##(l_{h})^3## ( where ##l_h## is Planck length ) ? We know that every information can be described in bits like volume is ##(l_{h})^3## so, In every bit of...

How many electron positron pairs are created every second in a cubic meter of vacuum?

I know that my title is not very suitable for this question, but I couldn't find right words to describe the situation.I read a book called '101 Quantum Questions ' and there writer states that when electron absorbs energy and goes higher energy level, we don't know when and where it will come...

Why is a sea of electrons present in a conductor? I read some where that they absorb a energy at normal temperatures and use it to get free electrons , but then why do they absorb energy while insulators don't??

so I am finishing up my studies of intro to quantum mechanics, and this is not in my book and looking at previous exams i have to know this for single electron atoms/ions. one of the problems was somethin like "the wave function of an electron is the overlap of the orbitals: Ψ=aΨ1s+i/√3Ψ2p+¾Ψ3s...

In SI units, the mass-to-charge ratio of the electron is $$\frac{m_{e}}{|q_{e}|} = \frac{9.11 \times 10^{-31} \text{kg}}{1.6 \times 10^{-19} \text{C}} = 5.7 \times 10^{-12} \text{kg/C}.$$ In which system of units do we have the dimensionless mass-to-charge ratio $$\frac{m_{e}}{|q_{e}|} \simeq...

This is not a homework, but a question formed in my mind after reading my textbook. Homework Statement Consider an electron (a charged particle) on a metallic equipotential surface. We know that all the points on the surface are equipotential, thus there will be no force on charged particles...

Homework Statement There is a sample problem in my physics textbook (Fundamentals of Physics, 10th Edition by David Halliday and others) which has some confusion in it for me. Please take a look at the snapshot I took, in the attachments. Homework Equations 3. The Attempt at a Solution [/B]...

Hi, How can I relate the beam energy of an electron beam produced by an electron gun to the accelerating potential? I realize that accelerating potential, initial energy (before acceleation), and losses by synchrotron radiation, etc, will play a part. I searched online and can't find much. Thanks

Homework Statement Homework Equations 1/2 mv^2 E = hf c = f (wavelength) The Attempt at a Solution 0.5 * (9.109 * 10^-31) * (6 * 10^4)^2 = energy energy = hf => f = energy/(6.626*10^-34) = 2.47 * 10^12 wavelength (m) = (speed of light) / frequency wavelength (m) * (1*10^9) = 121235.4 Answer...

I know this question might be too simplified but, What is the primary causes generation of light (electromagnetic waves) by electron? Is it vibration motion of electron or the motion of electron around the nucleus?

Homework Statement An electron in a cathode-ray tube is accelerated through a potential difference of 10 kV, then passes through the d = 2.4-cm-wide region of uniform magnetic field in the figure(Figure 1) . What field strength will deflect the electron by θ = 13 degrees?Homework Equations...

I have read in textbook that if a photon were to collide with a free electron it's an impossible situation for photon to get completely absorbed by an electron . The situation seems possible by conservation of energy but I am not able to understand the true reason behind the statement .is there...

Hi folks, I am reading "Purcell Electricity and Magnetism" and in the problem 1.77 he says: " Imagine a sphere of radius a filled with negative charge of uniform density, the total charge being equivalent to that of two electrons. Imbed in this jelly of negative charge two protons, and assume...

When a nucleus captures an electron from the innermost orbit, its proton number reduces one. Therefore, energy levels in the atom have to change accordingly, meaning all the electrons have to move lower energy levels. From this point of view, during an electron capture, can it be said that the...

Hi, I'm currently investigating magnetic fields/their cause. This has inevitably led me to learn all about electrons. Here I want to post my understanding on electron 'spin' so people can correct me if I'm wrong/help others get a better understanding. So I watched this YouTube video for...

Hi all, This is likely a naive question, following up on something @vanhees71 posted some time ago in another thread: My question is the following - if we take an electron that has, for example, absorbed a photon, is the portion of the wavefunction representing the electron in a lower energy...

To make antimatter you have to change the charge of proton and electron. So how do you do it

Hello, An electron accelerated through a pd of V volts will have a K.E = eV. Why isn't the K.E less than this considering that some of the work done by the field has been radiated as electromagnetic waves by the accelerating electron ? All insights very welcome.

Lets pretend there is a gun of some type that can fire electrons one at at time at a wall. The plane of the wall is oriented perpendicular to the x axis, which is to say that the wall is in the y-z plane some distance down the xaxis. There is no intervening screen with slits in it. We are just...

Homework Statement :[/B] Velocity of an electron at point A1 is Vo where cross sectional area is A. The velocity of electron at the end of contraction at point B where cross sectional area is 2A is V1.Find correct option a)V1< V0 b)V1= V0 c)V1> V0 d)V1<=V0/2 I have attached a picture of the...

Homework Statement Consider Compton scattering of a photon by a moving electron. Before the collision the photon has wavelength λ and is moving in the +x-direction, and the electron is moving in the −x-direction with total energy E (including its rest energy mc2). The photon and the electron...

I mean, we defined a second to be the duration of 9192631770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom [copied from wikipedia]. A meter is the distance traveled by light in 1/299792458 second. Why can't...

Homework Statement what is the value of ni for an electron that emits a photon of wavelength 93.14 nm when it returns to the ground state in the hydrogen atom Homework Equations planck's constant 6.63 x 10^-34 The Attempt at a Solution no idea [/B]

When a charge is rest w.r.t me no magnetic field is produced but when it moves w.r.t me then there exists a magnetic field, how?

Imagine we take a vertical, infinite wire and we let electric current pass through. The charges create magnetic field all around the wire. Now if we introduce an electron in the magnetic field, it will have a circular motion around the wire. The Lorentz force is not conservative, this means...

As we know from special theory of relativity, time flows slower for a moving observer. But also, thanks to gravity, time ticks slower and faster depending on whether the gravitational force is stronger or weaker. This f.ex. means that time will flow slower for a person living on the 10th floor...

Hello, I have a presentation tomorrow and in a segment, I talk about light absorption. It's more conceptual than technical. I did quite a bit of research on the topic but because of simplifying information I may have butchered the facts and written something wrong. Could anyone please confirm/...

Homework Statement I am having trouble with part d, where they ask me to prove that the wave function is already normalized The Attempt at a Solution But that clearly doesn't give me 1. I tried to use spherical coordinates since it is in 3D? Not really sure how to proceed. EDIT: I realize...

Homework Statement Consider an electron described initially by ##\psi = \frac{1}{\sqrt{10}} \begin{pmatrix} 1\\ 3 \end{pmatrix}##. A measurement of the spin component along a certain axis, described by an operator ##\hat{A}##, has the eigenvalues ##\pm \frac{\hbar}{2}## as possible outcomes (as...

http://www.nature.com/news/not-quite-so-elementary-my-dear-electron-1.10471 So when the electron is in the material, it separates into 3 different quasiparticles. But then it says that they cannot exist independently outside of the material. So does that mean the 3 quasiparticles are always...

What is the necessary and sufficient condition for an electron to radiate? How many methods to cause an electron to radiate?

Homework Statement Hey everyone, So my teacher assigned a mini project just before our finals and I was wondering if someone could look over my work and my calculations. I just want to make sure I understood everything since my final exams are coming. Here's the assignment. Compare and...

http://www.nature.com/news/not-quite-so-elementary-my-dear-electron-1.10471 It was found out that electrons are made of quasi particles. But kind of fields are the quasiparticles made of?

https://link.springer.com/chapter/10.1007/978-3-540-39664-2_1 http://iopscience.iop.org/article/10.1088/0031-8949/1988/T22/016/pdf In these two experiments done back in the 80's, electrons were trapped inside a penning trap for long periods of time. They were measuring the ratio of the magnetic...

Hey, I am studying Spin 1/2 system, the case of 2 electrons in a magnetic field, since we have 2 electrons, we expect that the matrix will be of the size 4x4, which is what I have got. As I know that I could use the density matrix to calculate the expectation values of any physical quantity...

I wonder if this question will make sense, but I will do my best shot: As the electron orbits around the nucleus, I imagine there are moments when it is too far away, so it starts to be "pulled toward" the nucleus. If it gets too close, it will be "pushed away". If it is in the orbital area...

Homework Statement A photon with the length of lambda hits a cathode perpendicularly to its surface. As a result, an electron leaves its surface perpendicularly to the direction of the photon. How much momentum was transferred from the photon to the cathode? The work function of the cathode is...

I am currently studying a Foundation Program, which includes chemistry. -I can easily understand the distinguishable characteristics between ground and excited state via writing the electron configuration. -But how can an tom changes from ground to excited state ? And can an atom changes from...

Homework Statement A problem of practical interest is to make a beam of electrons turn a 90∘ corner. This can be done with the parallel-plate capacitor shown in the figure (Figure 1) . An electron with kinetic energy 2.0×10−17 J enters through a small hole in the bottom plate of the capacitor...

Hi! I am trying to find the time for an electron to accelerate in a uniform electric field from u1 to u2. In the textbook, I found that time is found by integrating d(u/(1-u^2/c^2)^(1/2))=(qE/m_0)⋅dt and they get u/(1-u^2/c^2)^(1/2) = qEt/m_0 by integrating from t=0 and u=0 to t=t and u=u I...

Is Pauli Exclusion Principle alone responsible for electron degeneracy pressure?

https://scontent-ord1-1.xx.fbcdn.net/v/t34.0-12/17092376_1311006885612822_239104452_n.png?oh=72f2336f20f39bd399888901812eae3e&oe=58BAB2BF Hello PF friends. I know what the answer is, but I do not understand why the answer is. By the right hand rule I put my thumb west, but pointer up, and...

Assuming that the photon packet size is generally related to the wavelength of the light, say 500 nanometers and the electron approximate size of 2.82x10<-15 meters, how does the huge wavelength funnel it's packet energy to an electron approximately 1/17,730 th of it's size?