Quantum physics Definition and 729 Threads

I'm really interested in quantum theory and would like to learn all that I can about it. I'm looking books for learning quantum physics that contains derivation of Heisenberg uncertainty principle, dirac notation, pauli matrices, quantum operators, hawking radiation, etc. What are good books to...

Hi! I have been watching videos and a documentary about quantum physics on topics such as Schroedinger's cat, quantum entanglement and quantum teletrasportation. I am currently in high school, and don't have such competence in math needed to understand what exactly is quantum physics, and I am...

I am still in secondary school so I probably shouldn't think about things this complicated (at least that's what it seems to me, complicated), but please correct me if I'm wrong. If I recall correctly, the position of an electron is never certain, and always based on probability, unless...

Homework Statement This integral has to do with the probability amplitude that a free particle at position x0 is found at x at some time t. With H = p2/(2m), this involves evaluating the integral 1/(2π)3∫d3p e-i(p2/(2m))t eip(x-x0) The answer is (m/(2πit))3/2e(im(x-x0)2)/(2t) 2...

Hello :) Before I get to my topic I want to adress that I am new to this website and wish to apologize if my thread is incorrectly placed. I am interested in black holes and lately I have been trying to find some math which lays the basis for a black hole firewall. Sadly I haven't been able...

I was looking at the moon rising and noticed that it starts off quite yellow/orange and gets more and more white as it reaches the middle of the sky. Why does it look bigger? I'd imagine it's something to do with refraction, but how exactly does it work? Does the moon look more orange closer to...

So I've always been fairly good at whatever science I learned in elementary and middleschool (which was mostly biology), and I've fairly enjoyed it, but I've only recently started really learning, and I've come to love it. I've especially found quantum physics interesting, however, seeing as I...

Hey, I would like to showcase my experiment I'm doing. I'm 16, in high school, and the only science I know is chemistry. But that was a default class. I'm learning about Quantum Physics on my free time. and would very much like to become a scientist in that field. To start off this is kind of a...

Can any expert help me in explaining how this example below get the reduced density matrix from the density matrix in bipartite system. $$\rho =\frac{1}{4}\begin{pmatrix} 1 & 1 & cos(\frac{\alpha}{2})-sin(\frac{\alpha}{2}) & cos(\frac{\alpha}{2})+sin(\frac{\alpha}{2}) \\ 1 & 1 &...

Sorry, this might be a question you can only answer with speculation, but if anyone has any idea of how close we are to teleportation of inanimate objects or creating portals, I would love to know. I have always found teleportation and portals to be super cool. From what I've heard, in order...

Hi, I just completed my second year of my physics undergraduate degree. And recently did a course on Quantum Mechanics. I have a few questions regarding the basic theory and postulates, probably, because due to lack of full clarity. So, Consider a wave function ψ(x,o), which is well behaved and...

So, I am not an expert in quantum physic, I just watched a lot of videos about it. If I understand correctly, particles do not have a particular position as long as you don't observe them. With a certain equation, we can draw a cloud of probabilities which describes how likely the particle is...

Hello Everyone! My name's Christina and I work at the Everyman Theatre in Liverpool... We have a show coming up in the main space at the beginning of July that's going to be performed by YEP (Young Everyman and Playhouse)... and hopefully it's going to be a love story about all things Physics-y...

I heard a lot of this "Quantum theory defies the human logic, it's totally illogical but it works!" and I'm trying to understand whether this is true or not. I don't mean by logic some mind blowing stuff, like teleportation is possible. I mean the kind of logic that would be difficult or...

Homework Statement √[/B] A particle in an infinite square well has the initial wave function: Ψ(x, 0) = A x ( a - x ) a) Normalize Ψ(x, 0) b) Compute <x>, <p>, and <H> at t = 0. (Note: you cannot get <p> by differentiating <x> because you only know <x> at one instance of time)Homework...

Hi, My Modern Physics lecturer is of the opinion that the energy dissipated during exothermic reactions is due to infinitesimally small change in mass of the reactants. Similarly, he said that an infinitesimally small part of the food we eat gets converted into the energy using which we perform...

Homework Statement Metal Surface is illuminated with 200nm wavelength light. Work Function of this metal is 3.0eV and its electric potential is 5V lower than a point of infinity. Determine max K.E of photoelectrons, which are just emitted from the work surface. Homework Equations K.Emax= hf...

Homework Statement Comment how the energy and wave functions of the electron would change in the case of a finite dept quantum well with the same width. Homework EquationsThe Attempt at a Solution I feel completely clueless as how to approach! :( * The full question can be found in the...

Hello, my name is Brent I am very interested in Quantum Physics as well as Astrophysics. Is their anything I should know pointer or tips. Thanks.

Considering how Heisenberg's uncertainty principle is applied to a top-hat wave function: This hyperphysics page shows how you can go about estimating the minimum kinetic energy of a particle in a 1,2,3-D box: http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/uncer2.html You can also...

Homework Statement A beam of ultraviolet light with wavelength of 200 nm is incident on a metal whose work function is 3.0 eV. Note that this metal is applied with +1.0 V with respect to the ground. Determine the largest kinetic energy of the photoelectrons generated in this process. Homework...

Homework Statement A He-Ne laser emits red light of the wave length lambda =632.8 nm with a beam diameter of 2.0 mm and a power output of 1.0 mW. (a) What is the intensity of this laser beam? (b) What is the magnitude of the momentum of each photon? (c) How many photons does this laser emit...

< Mentor Note -- thread moved to HH from the technical physics forums, so no HH Template is shown > Hello guys, i need some help in clarifying a question. A beam of ultraviolet light with wavelength of 200nm is incident on a metal whose work function is 3.0eV. Note that this metal is applied...

some cool stuff happening here

I want to start learning quantum mechanics but i have no idea where to start . I want to know which other fileds and physics branches i have to study before quantum mechanics and if i want to go more deeply for this (like taking a graduate course ) what should i study before this in physics math...

i am completely lost. there is an integral in my textbook in fermi dirac statistics whose result is written directly and am not able to understand . it is ∫⌽(u) du /exp.((u-uf)/kt) + 1 from 0 to ∞ expanded by tayor's series to give...

Homework Statement Given the following wave function valid over -a \le x \le a and which is 0 elsewhere, \psi(x) = 1/\sqrt{2a} Find the uncertainty in \left<\left(\Delta p\right)^2\right> momentum, and the uncertainty product \left<\left(\Delta x\right)^2\right>\left<\left(\Delta...

Homework Statement Im being told that each quantum of light(a photon) has energy which is equal to hf. (E=hf). Now what I don't understand is how can a photon have a frequency? Shouldnt the light wave(which is made up of quanta called photons) have the frequency and not the photon itself? How...

degeneracy,this word appears in my textbook many times,but i could not understand what it means in quantum statistics.also in my textbook it is said in bose-einstein statistics that " the deviation from perfect gas behaviour exhibited by bose-einstein gas is called gas degeneracy".but i can't...

Before I begin this thread I must confess to nearly complete ignorance of Quantum Physics, or for that matter most any technical science.(I'm somewhere between a consumer and a parasite). That being said I came across this JPL link and it caught my attention, seems to be some groundbreaking...

Hi, I am studying civil engineerin. I wonder if learning quantum physicist could be worth it for my career. I know that as an engineer I can get a master degree in physics, which have a lot of topics of modern physics. Do you think it could be a good idea? I mean, these new knoeledge is helpful...

Homework Statement (a) Show that in the Bohr model, the frequency of revo-lution of an electron in its circular orbit around a stationary hydrogen nucleus is f = me4/4ε02n3h3 (b) In classical physics, the frequency of revolution of the electron is equal to the frequency of the radiation that it...

Hello, What would be the best online resources for learning modern physics and quantum physics (at the undergraduate level). Also, what is the highest math that would be necessary? I think the only one I am lacking is PDE but I can self study that one as well if necessary. Thanks in advance.

I know light has wave particle duality, I understand these two points very well, 1. Light moves as a probability function, taking all the possible paths at once. The alternate paths cancel themselves out, resulting in a particle-like combined motion. 2. When relatively close to an edge, some...

Leonard Susskind says so. But I don't see it. Yes, the present "here and now" is computed by nature from the events lying in its past light cone + the laws of nature. If we assume a deterministic universe, the present "here and now" contains the information from the events in its past light...

It's often said that modern electronics is based on quantum mechanics. As far as a I can tell however, detailed understanding of quantum mechanics isn't needed to, say, design a transistor. Although quantum mechanics sets a lower bound on the size of electronics, this would be obvious...

The article on undecidability of presence of spectral gap by describing its microscopic structure seems to contradict the fact that we can decide whether a CNT is metallic or semi -conducting by checking its diameter and its twist.

I studied this from Griffith Chapter 2, with the algebraic (raising and lowering operator) method, we reached the ground state by setting a_Ψ0 = 0 , then we got what the ground state is, and then plugged it in the Schrodinger equation to know the energy, and it turned out to be 0.5 ħω. My...

Homework Statement Show that phi_n will find the proper phi_4. IE: show that it gives the correct normalization constant. Richard Liboff...chapter 7 Homework Equations A_n = (2^n * n! * pi^1/2)^-1/2 The Attempt at a Solution I don't know where to start really. I tried some things with <...

Whole my life I have been interested in Quantum Physics. I have a bachelor degree in IT. I did not finish my studies. I have always been quite sloppy in studying in school. As a result, my mathematics skills are terrible. I often get pointed out on this forum that I better start with the...

Any recommended books, published pieces, online articles, youtube videos to help understand (or at least introduce me) Quantum Physics? Hell, a college thesis would suffice.

Hi all, I am reading the book "Emperor's New Mind" and have a question related to time asymmetry in state vector reduction (p.458) in quantum mechanics. Consider the following situation, as presented in the book: Suppose I have closed room with a lamp L, which emits light in some fixed...

I was curious about what forces can be applied to a molecule to cause a rotational emission.

hello, I have come across "quantum physics" during the curriculum of an Inorganic chemistry course. and since the topic is too broad, I'm confused a bit about what exactly do I need to know ( or to which extent should I learn about this theory). we are studying the historical development of the...

According to quantum physics, things don't exist until being observed/measured. If this is the case why can we predict the same reality being generated? For example, if the moon doesn't exist when it is not looked at, then why does the moon keep appearing when we do look at it. Is "reality"...

Homework Statement Show that ∫ ψ1(x)*ψ2(x) dx = ∫φ1(k)*φ2(k) dk (Where the integrations are going from -∞ to ∞) Homework Equations 1. Plancherel Theorem: ψ(x) = 1/√2π∫φ(k)eikx dk ⇔ φ(k) = 1/√2π∫ψ(x)e-ikx dx The Attempt at a Solution It is clear that Plancherel's theorem must be used to...

Homework Statement The work function (energy needed to remove an electron) of gold is 5.1 eV. Two pieces of gold (at the same potential) are separated by a distance L. For what value of L will the transmission probability for an electron to cross from one to the other be T≈ 10-3? Assume that G...

why quantum physics like a math theory till a physics theory,it never describe a of phoneme ? it write equation between many Hypothetical objects!

Hello, sorry if I created new thread that is already open, but I did not find answer. I would like to ask you about measurement problem (double slit experiment) and many worlds. When interference pattern is created, the dot on screen just show us in which branch or world we are. But if we...

Pretend we have a multi-slitted grating whose slits are infinitesimally small. We On each slit is a detector. If we shine (UPDATE) light monochromatic light through the grating, what distribution pattern occurs on the screen past the grating? I understand the train of thought to a slight...