Measurements Definition and 382 Threads

When a photon encounters a beam splitter, say a half-silvered mirror, there is a 50-50 chance it will be reflected or passed (tunneling). Does being reflected/passed constitute a QM "measurement"? Thanks in advance.

Homework Statement A furlong is and old British unit of length equal to 0.125 mi, derived from the length of a furrow in an acre of plowed land. A fortnight is a unit of time corresponding to two weeks, or 14 days and nights. Find the speed of light in megafurlongs per fortnight. (one...

Homework Statement 1) What is needed for an ammeter to measure current accurately? 2) What is needed for a voltmeter to measure the potential differences in the circuit accurately? 3) How can you construct an ammeter from a resistor and a galvanometer? 4) How can you construct a voltmeter...

Just a thought: If we could identify the position and velocity (via weak measurements) of a particle at some instant, and its future evolution is fully determined (at least in principle, not in practice), then can we extrapolate this to surmise that all events are are inherently deterministic...

hello. can anyone help me find information about "dynamic hardness measurements" ? a direction to books or websites will be very helpful... thanks

I am a little confused on the difference between statements of electrical output when the talk of gigawatts or gigawatt hours? for the formula P=ghrk where P is power in kilowatts g is gravity (9.8) constant r is flow of say water per second k is efficiency...

This has been very comfusing. Is the error in taking a reading the smallest or half the smallest division? Say a standard 30cm ruler, you can judge to nearest 0.5mm but since you take 2 readings you need to double the error. But then in titrations using a lab burette you count the titre as half...

hello all, i am a beginner student in this field at NHTI in concord NH , the problem i am having is that my multisim program measurements for a simple voltage point at a resistor is inconsistent with the actual measurement that i got in the lab...? why is this? is my math wrong? here i will give...

Another confusion: How many measurements is "many"? Since quantum mechanics gives only statistical prediction, we actually need numerous measurements to verify the theory. But how many measurements will make it statistically meaningful? Let's say we want to verify the uncertainty principle, we...

Can anybody let me know in detail about time and its measurements.

Hi Can anyone help me to solve the following question; Note: in both equations the +/- is written above and below of each other without the '/' sign. Thanks.

For an exam I am studying for, I have to understand the effect of measurement tolerance, calibration accuracy and time-related drift on frequency measurements. Im aware that the time-related drift is due to the oscillator frequency becoming less accurate (due to continuous crystal vibration)...

In the beginning there were only probabilities. The universe could only come into existence if someone observed it. It does not matter that the observers turned up several billion years later. The universe exists because we are aware of it. — Martin Rees Professor of Cosmology and...

Homework Statement Consider a state |psi>, and two non-commuting observables A and B. Now study the following chain of measurements: (i) On |psi> a A [sic] measurement gives the result a1, and a subsequent measurement of B gives the result b2. (ii) On |psi> a B measurement gives the result...

The classic reference on this is Bell's (highly recommended) polemic "Against measurement", which is in the 2nd edition of Speakable and unspeakable in quantum mechanics (but not in the 1st edition; it can also be can be found in the original, Physics World 3 (August 1990), page 33). A quote to...

Hi all, this is my first post to the forum. I've been thinking about a mechanism that can't work, but I can't figure out why not. Here is the idea: 1) If I have two wires parallel to each other on a table and I run a current through them, they will be attracted to each other. I believe...

In this example I make 2 assumptions 1. if an object is moving through space at time T0 it will be at point x,y,z,T0 and at a different time T1 it will be at a different position x,y,z,T1. The other assumption I make is that light is non ballistic. see the associated pics Referring...

I started this thread to continue the following discussion from the thread: https://www.physicsforums.com/showthread.php?p=2203566#post2203566" But you and Weinberg are both making a mistake in assuming ontological status to both the collapse of the wave function and to entanglement...

In conducting an experiment to measure the bandgap of n-type Ge using the 4-probe method, heating the sample and measuring the change in voltage across the probes as it cooled, it was necessary to change regularly between the milliammeter and the millivoltmeter setting on the instrument to...

I am asked 'name 3 example of interactions that can be measured by AFM techniques', then followed by 'name 3 examples of the types of interaction forces that are measured with AFM'. 1) Aren't interactions kinda the same as interaction forces? 2) I thought there is only one force, van de...

Homework Statement The spring of a pressure gauge has a force constant of 1250 N/m, and the piston has a radius of 1.20 cm. As the gauge is lowered into water, what change in depth causes the piston to move in by 0.750 cm? Homework Equations F = -k\Deltax \frac{F}{A} = Y\frac{\Delta...

Dear All, I would like to least square fit a number of measurements using several nonlinear functions with shared parameters (similar to the advanced fitting in Origin) using Mathematica. Therefor I would be interested in an Algorithm like Gauss-Newton that fits several data-set to several...

Discuss the effects of the following sources of errors on Measurements of length & mass. and suggest metods to overcome them: 1- Existing of a dust on both the sample and the measuring devices. 2- Irregularity of the samples. 3- Slope of the balance from the horizontal line. 4- Other...

Query: Given a three- dimensional wavefunction (phi) (x, y, z), what is the probability of simultaneously measuring momentum and position to obtain the results a < y < b and p' < Pz < P" ? I know that integration of the square norm of the wavefunction of the region under question...

Homework Statement OK, so assuming we have a physical observable with three values, a(1),a(2) and a(3), and there are given matrices for the measurement operators M(a(1))...M(a(3)). How does one actually go about finding a(1),a(2) and a(3) given the matrices?The Attempt at a Solution These...

Homework Statement Light passes through a 220 lines/mm grating and is observed on a 1.4m wide screen located 1.2m behind the grating. Three bright fringes are seen on both sides of the central maximum. What are the minimum and maximum possible values of the wavelength? Express your answers in...

I was wondering if anyone has suggestions in terms of wireless transmitters/receivers for a system that will have over a dozen temperature measurements (either thermocouples or RTD's). I have no idea where to even begin looking. Thanks,

Homework Statement The x coordinate of an electron is measured with an uncertainty of 0.200 mm. What is v_x, the x component of the electron's velocity, if the minimum percentage uncertainty in a simultaneous measurement of v_x is 1.00 %? Use the following expression for the uncertainty...

Homework Statement i am trying to work out the uncertainty of some measurements but i don't know how to, i tried finding some info on it online but i cant, well these are my 10 measurements 9.13mm 9.12mm 9.13mm 9.12mm 9.12mm 9.13mm 9.13mm 9.12mm 9.13mm 9.12mm Homework...

Will an accelerating observer obtain the same value for light velocity as one at rest or moving at constant velocity? Will the measurement be the same for linear and radial (circular motion) acceleration?

Homework Statement This is a true or false question on a practice test. I'm having a hard time making sense of it. Here it is: Two operators A and B do not share eigen states a(n) and b(n) where n=1,2,3,etc. A measurement of A is made and the system is found to be in state a(1). If the...

Homework Statement Hi all. My question is best illustrated with an example. Please, take a look: Let's say we have particle in a stationary state, so \Psi(x,0)=1\cdot \psi_{1,0}(x) with energy E_{1,0}. Now at time t=0 the Hamiltonian of this particle changes, since the particle gains some...

Please, please look at the document I've attatched. My questions are: Have I done the calculations correct? Do I have correct significant figures? I have to discuss the random and systematic errors... but I don't know what ones that we've had. Help? And they tell us to point out...

Homework Statement a. How wide is the gap between tiles in centimeters? b. How wide is the gap in inches c. How many algae-thicknesses is the gap between tiles Homework Equations The Attempt at a Solution First off, I just want to know if I did a and b correctly. To set up...

In general, are the measurements of current or voltage more accurate? From our lab experiments, it seems that voltage is more accurate. I'm curious as to why this is the case. My guess is that because current itself is the measurement of the flow of the electric charges it would be more...

Homework Statement The Apollo 11 astronauts set up a highly reflecting panel on the Moon's surface. The speed of light can be found by measuring the time it takes a laser beam to travel from Earth, reflect from the retroreflector, and return to Earth. If this interval is measured to be 2.51...

They say often that light only travels at light speed in a vacuum. That it slows down in air and water. I do not think this is true - correct me if I am wrong as I usualy am :shy: All atoms are vacuum. Light is energy that is not made of atoms, or in other words it is smaller then atoms if...

Dear All I will be grateful for any idea on how to measure electrochemically the charge carrier in an electrode say working electrode made of Al. Thank you from advance Shay

How is strong nuclear force measured?

Hi Can anyone tell me how magnetic field strength decreases with distance in free space? If the source was effectively a point souce in a plasma, what would the field strength be at a specific distance? Is it source field strength/4 pi r sqrd? As an example if the source was 1T, what...

http://postbiota.org/pipermail/tt/2007-May/000515.html Does anyone know what happened with these experiments?

Say we have a BELL state |B00> = cos(a) |00>+ sin(a) |11> then for a (just one) pair of entangled particles, we keep one on location q, the other one in location w; the one in q forms a system Q, the one in w forms W. ( 'x' in a function like |v> x |w> indicates a tensor product)...

To all the engineers or the enginnering students out there. How do you give the definition to one meter (1 m)? More: How much do you weight in Newton, slug, and pound-force (lb_f)?

[FONT="Times New Roman"]Hey, Simple questions, and hopefully I can explain my query a bit better than others I have made. I'm just trying to think of any advantages for using radians instead of degrees? I know/think that degrees are an arbitrary unit but cannot think of any reasons for using...

Does anyone know why we prepare F- containing solutions with plastic beakers and cups instead of the regular glass beakers before measuring the responses with F- ion selective electrode Is it because F- in corrosive? where can i find infomation on this? Thanks a lot~

okay, good. actually at another time i was staring at the more general equation and had a few questions regarding it. so 1/H is the Hubble Time and about the age of the universe (maybe a milli-smidgen longer). this has been measured independently (from astronomical observation), right? and...

Are all observations of quantum nature, that the macroscopic universe is just a montage of microscopic interactions we have experienced?

Can operators describe a single or many measurements at a single time? i.e. a stern-gerlach atom deflection experiment where we can measure "up" deflection and "down" deflection or just "up" deflection. I think I'm pretty confused..

I'm not sure which location to post this in; but since it deals with the very small (sub-atomic), then I'll post it here. Does anybody know just how precise they can measure time? Can they measure seconds down to 50 yotta seconds (10^{-24})? I have a theory (well, not quite that far yet...

I recently watched a program called 'Atom' on bbc4 that said something along the lines of: "If you want to strike fear into the eyes a physicist; mention the measurement problem" - What is the measurement problem and why is it such a problem?