Measurement Definition and 1000 Threads

I want to prepare murexide indicator for Ca measurement using EDTA titrimetric method. I am following the procedure set by the American Public Health Association (APHA), however, I only have murexide diluted with K2SO4 (1:250). I want to know if I can use this as a substitute, and if yes, how...

All these videos and articles about the Double Slit Experiment say that if we "look" where the single photons go, they act like particles and if we don't "look" they act like waves, creating the interference pattern... BUT What does it mean to "look"? We're not using our eyes or any camera...

Dear all, I am trying to use Van der Pauw method to measure some samples, however I cannot get where in calculations van der Pauw method includes size of the sample. F.e. if I have circle with diameter of 2 cm or 5 cm there must be a difference right? Can anyone explain to me why or why not...

The experiments that have been done to demonstrate that entangled particles are correlated (or anti-correlated) have been designed so that Alice and Bob's measurement events are intentionally space-like separated. Thus demonstrating that the "ghostly action at a distance" is supraluminal or...

Can we measure 'absolute entropy' of a system. Also can entropy become zero at 0 kelvin.is it possible only theoretically?

Homework Statement Homework Equations I solve the (a) , using even,odd function. So, C=1/a The Attempt at a Solution I don't know how to approach (b). I think that 'total energy of the system' doesn't mean expectation value, how can i get total energy and probability of them?

Supposing we have 2 circles in a 2 d space that can bounce off each other like balls. These circles are made of an infinite number of points. We put the centre of each circle on a line and send them towards each other along the line. Are they going to bounce off keeping their trajectory on the...

A delightful video here A lecturer derives special relativity in a world of bats and echo location using a bat (sound) clock. All communication is limited by the speed of sound. (so a parallel of our world and light speed communication) He ends up observing that in no cases for any observer...

I am new here so I will start with a warming up question :) My question is very trivial here we go: In double slit experiment when shooting one photon at a time, we get interference pattern. Then when we put a sensor at one of the slits the interference pattern disappears because we now know...

On wiki measurement is defined as: Measurement is the assignment of a number to a characteristic of an object or event, which can be compared with other objects or events. So a number. For scalars, I agree because they are described by a single number. But what about vectors? They have...

Hi. I'm afraid I might just be discovering quite a big misunderstanding of mine concerning the meaning of the expectation value of a commutator for a given state. I somehow thought that if the expectation value of the commutator of two observables ##A, B## is zero for a given state...

Hello. So one of the axioms of measurement science is that every measurement we make is an approximation and can never reflect the true magnitude of a physical phenomena. We would then go on to teach that there is a certain "true" magnitude which is something that experts or majority would...

I have done experiements on a grinding machine and have collected the data of grinding wheel profile (using a laser sensor). The raw data consists of info on grinding wheel profile, waviness and roughness (because of abrasive grains). I would like to process the colelcted raw data. I want to...

I have a technical question, for research purposes. I have LED that we probe in AC mode. To measure the applied voltage in AC and the light-response in AC is no problem. However I would like to measure the current going through the device as well and I would like to link it to an oscilloscope...

Hello I am currently have difficulties trying to measure dc-modulated voltages while applying a dc current, via Sr830 Lock-in Amplifier (LIA). Basically, I apply an 2 GHz ac current (amplitude modulated@10kHz and referenced to the LIA for lock-in measurement) and a dc current to my DUT...

I am trying to find examples problems on thermal expasions related to the subject of measurement technique Google but I can't find them.. I don't know exactly what could be asked but the problem will be related to: "expansion of measurement device" is given, and "expansion of measured...

I have a question on my homework set and I'm not sure the principle behind it: 1. Alice measured an observable F (a matrix) and passed the measured system immediately to another experimentalist, Bob, who is going to measure another observable G. Alice claims that she can deduce the experiment...

I was going through Figure S9 in this paper yet don't quite understand how one can assign a probability density to a dynamic spectrum measurement as the authors do. To my knowledge, a dynamic spectrum simply displays the intensity for each frequency channel against time as shown in Figure 1C of...

Quantum mechanical foundations are usually phrased in terms of measurement. I believe this is the main cause why these foundations remain shaky after almost 100 years of a good mathematical basis. Classical mechanics never had any reference to measurement in its foundations, and hence it was...

Hello, I have a set of data, two columns, and each datum has its measurement error like illustration shows below: x | y --------------|----------------- x1+/-xe1 | y1+/-ye1 . | . . | ...

Part of the question says: An unit cell has a cell edge of 288 pm. I got to the part where volume (288 pm)^3 = (288 x 10^-10 cm)^3 I have no idea how that equals 2.39 x 10^-23 cm^3 Only the Bold part ^

If you measure the height of a mountain, you compare it's height with the sea level. But on let's say mars, how do you measure height when there is no sea to compare with? For example: Olympus Mons is considered to be the tallest mountain or vulcano in the solar system, but what is the level on...

What is the difference between the noun "instrumentation" & "measurement"? Thank you.

Hello all, I'm using peltier modules (also called thermoelectric modules) for a student project. If you're not familiar, they are small semiconductor devices that when heated on one side and cooled on another, power flows due to the Seebeck effect. I'd like to measure power coming from...

My question is as follows, given a hermitian operator, what's the physical difference between performing a measurement on a particle to get an eigenvalue of said operator and acting on the state of the particle with said operator? What prompted my question is the swap gate used in quantum...

Homework Statement I have only repeated a measurement once, I cannot assume it is distributed as a Gaussian because there is so few data. How can I estimate its combined uncertainty? The Attempt at a Solution Total data: x1, x2 I calculated the individual uncertainties in x1 and x2 using error...

1. Within the framework of a Hilbert space for an atom one cannot find an observable in the sense of ''self-adjoint Hermitian operator'' that would describe the measurement of the frequency of a spectral line of the atom. For the latter is given by the differences of two eigenvalues of the...

Basically, I found the energy of a photon using its frequency ((6.8*10^15) and E=(3.6496394*10^-16)) and so I then used "p=E/c" to find the momentum and got 1.2173887*10^-24 however I don't know the measurement of the momentum. Is there a better equation to use to find momentum, and what would...

Hello! I'm an Engineer by profession with less knowledge of physics, so please be basic with me. After recently being intrigued by the double slit experiment, I started to read more and more about the same. At most of the places, it says that as soon a sensor is kept near one of the slit to find...

Do we yet have an explanation for the Measurement Problem that Einstein would have been satisfied with?

I understand that c is the "ultimate speed" and that it is a result of the fundamental constant, the permeability of free space. But if this is a constant only to a "stationary" frame of reference, how can we accurately measure it from Earth? Since Earth is moving relative to a supposed "fixed"...

It seems to me that we don't measure a particle because a particle doesn't have an objective existence independent of the wave function or does it? The wave function in this case would have to be real because you can't have probability without the underlying possibility of a specific outcome...

Hello, I'm interested in building a small non-invasive battery powered device that wraps around a pressured 1/2" pipe for measuring potable water. From https://en.wikipedia.org/wiki/Magnetic_flow_meter and watching youtube videos, it seems they all use electrodes which contact the liquid...

As I understand it, the proper length, ##L## of an object is equal to the length of the space-like interval between the two space-time points labelling its endpoints, i.e. (in terms of the corresponding differentials) $$dL=\sqrt{ds^{2}}$$ (using the "mostly plus" signature). Furthermore, this is...

Homework Statement What's the answer to (0.781±0.002)/(0.551±0.002)? Well, here is the answer (1.417±0.008) that professor Walter Lewin said in one of his videos. I checked this in an online uncertainty calculator and it turned out 1.417±0.006. Homework Equations n/a The Attempt at a...

Homework Statement Suppose we have a wavefunction with n=4. If we measure the orbital angular momentum along the z-direction(no spin in this problem) and get 2*hbar then what are the possible values of the total angular momentum and what is the most general wavefunction after the measurement...

We know that Schwarzschild metric describes an asymptotically flat spacetime. This means that far away from the event horizon we can safely interpret the ##r## coordinate as distance from the center. But when close enough to the event horizon the curvature becomes significant and our common...

Homework Statement What is your average reaction time? What is the uncertainty? Homework Equations To find time I used the following equation: t=\sqrt{\frac{2(\frac{D}{100})}{9.81}} D is measured in cm, hence the division by 100 (to get meters). 9.81 is acceleration due to gravity (this comes...

I am "proofing" various pH probes in an in-situ fresh water environment--this is a low electrolyte environment where such probes typically do not perform very well. I want to routinely sample the water and obtain accurate pH data for comparison. Can someone enlighten me on the what modern (non...

Hello, Recently, I have been trying to work on some philosophy that I am developing, and the subject of measurement has come up. My question goes a bit like this: Suppose that it turned out that when you measure point A to point B as exactly 100cm (one metre), there are actually three...

Say a particle was measured to be at a point C. Immediately after this, if i make another measurement, its given in griffith's book that the particle will still be found at C. Isn't this only possible if the particle was at rest?

Hello everyone. What measurements have been done of the Higgs self-interaction? If nothing has been done yet, what are the relevant groups and research articles describing the progress of work in this direction? If this has been done, I would love to know the references. Thanks!

Hello all, I have a 1kw 3 phase 10 pole servo motor which is powered from 240 volt ac single phase supply via an invertek p2 controller/inverter. The motor is only operated for short high speed bursts and I would really like to be able to measure the power usage of the motor using formula and...

I have a micro-controller with 10 bit resolution. How can I convert the voltage or digital output of the microcontroller to a Lux reading ?

Hi all My question: One of the four Bell's state are measuring in the Bell basis. Whether the result of measurement of this one of the four Bell's state will be the same Bell's state (just that Bell's state which are measuring) ? The each of four Bell's state is a quantum superposition of the...

Does a 'weak measurement' on the spin of an electron in a pure state put the electron in a mixed state of the previous state and the state of the measurement axis of the measurement?

Hello everyone. I've gotten interested in quantum mechanics after binge watching a ton of documentaries about it. I've grown particularly interested in superpositions and the measurement problem. I'm not very good at math, so I can't understand the math behind it, but I like to take the...

If we assume there is no counterfactual definiteness, would that mean that measurements on entangled particles needn't be correlated, for if you don't compare the results, you just don't know if they do?

I have a question that seems to reflect my main concern with QM. Here it is: Consider a series of polarisation-entangled photon pairs that are sent in opposite direction to two measuring devices (e.g. at opposite ends of the universe). The measurement consists of detection of a photon after...