Questions tagged [measurements]
The measurements tag has no usage guidance.
829
questions
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1answer
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What can be measured in quantum mechanics and how?
This is a question about bridging reality to theory.
In learning QM theory, we learn a bunch of stuff about observables, like their operators, that two quantities can be measured at once if their ...
0
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1answer
26 views
Significant figures in complex calculations
In my physics book it is written that ' In any involved or complex multi-step calculation, you should retain, in intermediate steps, one digit more than the significant figures and round off to proper ...
0
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1answer
67 views
2019 Higgs Boson Mass?
Wiki, based on the 2018 Particle Data Group, gives the Higgs boson mass as $125.18 \pm 0.16$ GeV$/c^2$. OK.
However, 2017 ATLAS gives a combined value of $124.98 \pm 0.28$ GeV$/c^2$.
So what is ...
0
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1answer
15 views
Is it possible to measure the amplitude of a magnetic field independent of the orientation?
The strength of a magnetic field can be measured as strength in a specific direction.
We can calculate the strength of a magnetic field along the field lines from measuring the strength in x,y,z ...
1
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2answers
27 views
Light Polarizer for Photons
This is maybe a noob question. I read that if unpolarized light is passed through a polarizer that only allows vertical polarization, then if this light is passed through a diagonal polarizer, only ...
1
vote
1answer
19 views
Does a maximum thermometer assume a room temperature?
Consider a liquid-in-gas maximum thermometer. That is usually conventional thermometer designed for measuring body temperature.
Wikipedia says:
One special kind of mercury-in-glass thermometer, ...
-3
votes
3answers
136 views
Why are speeds of different EM waves in vacuum not EXACTLY equal?
It is said in my textbook (reference below) that the different waves of the Electromagnetic Spectrum have velocities almost equal to each other. (Variations are within a few m/s according to my ...
3
votes
1answer
83 views
How to know that scientific instruments work?
While reading Zimring's book, What Science Is and How It Really Works, I came across some words on being skeptical about scientific instruments on p.183-184:
"The extent to which such instruments ...
1
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1answer
17 views
Uncertainty and error in a measurement
I do not find a clear and simple explanation of the difference between uncertainty and error of a measurement.
Basically, in a measurement, uncertainty is defined as the standard deviation of the ...
-1
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1answer
32 views
Significant figures and precision
Which of these two measurements is more precise, 5.1 cm or 0.002 ? As per concept of significant figures 5.1 cm is more precise because it has two signicant figures while the other oone has just one
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0answers
27 views
Principle of a pyrometer
How does a pyrometer work? Especially how do I ensure that the temperature of a single spot is measured (where the laser points at)?
Here is a scheme of the structure but I guess it's not really ...
0
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3answers
41 views
Are interference patterns the basis for all other measurements of light frequencies and wavelengths?
The wavelength or frequency of monochromatic electromagnetic radiation is determined indirectly by calculations on the interference or diffraction pattern. These patterns are generated by gratings, ...
20
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4answers
1k views
How is the speed of nucleons in the nucleus measured?
This article claims that "nucleons in a dense nucleus exceed 25 percent of the speed of light".
How do you measure or infer the speed of nucleons in the nucleus?
Note added later: I'm looking here ...
0
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1answer
25 views
Why does a photomultiplier tube (PMT) traditionally present better signal-to-noise ratio (SNR) than an avalanche photodiode (APD)?
Empirically, a photomultiplier tube (PMT) is said to present better signal-to-noise ratio (SNR) than an avalanche photodiode (APD). Some materials say that it is attributed to the higher gain and ...
0
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3answers
45 views
Use of significant figures in lab report calculations
I am currently doing a lab report that involves multi-step calculations. The values σ(mean, visual) and σ(mean, auditory) are calculated to be 0.004051s and 0.004917s. Since the number of trials (27 ...
0
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0answers
12 views
Methods of Subnanometer Distance Measurement
How can one measure distances down to the ~0.01nm resolution using standard equipment such as LEDs, lasers, photodiodes, interferometers etc...?
A pulsed diode could be used as a measurement device ...
0
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1answer
22 views
Is Bourdon tube affected by the cross sectional shape of the tube?
I've been searching for the working of pressure measuring tools , and i know that what makes the bourdon tube straighten is the distribution of the pressure on its walls .so
my question is , in ...
1
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1answer
57 views
What does “An experiment performed with certainty has results with uncertainty.” mean? [closed]
A physics book says:
An experiment performed with certainty has results with uncertainty.
What does this mean?
1
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1answer
36 views
Measuring acceleration due to gravity in the lab
I am measuring the acceleration due to gravity in the lab with an electromagnet apparatus.
My textbook says to take the average time for a number of falls (keeping the height constant of course).
...
0
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1answer
22 views
How to measure the microscopic surface area of a textile?
How to measure the microscopic surface area of something like a piece of cloth?
By microscopic, I mean on the level of fiber surface, not the area that would be measured by using a ruler on the piece....
0
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0answers
13 views
Transformation to get rid of distribution multiplets
Are there any well-known distribution transformations that account for doublets, triplets, higher multiplets due to time series independent peaks occasionally being too close to resolve? I feel like ...
2
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0answers
55 views
How to estimate the mass of an incoming asteroid?
A second galactic visitor has just been observed: see this link.
For a mass which is small enough to have no noticable effect on other masses, is there any other way to infer the mass? Its own motion ...
-3
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1answer
46 views
Changes to Planck constant historically [closed]
I looked all over to get the various accepted value of the Planck constant since 1900. But there is never any record about the history of this mysterious number.
0
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1answer
36 views
How to build a particle detector, given a desired probability of detection [closed]
Suppose that the average flux of cosmic rays at sea level on an horizontal surface is $$\varphi = 1\, {\text{cm}}^{-2}\,{\text{min}}^{-1}$$
and that we can take this value without error.
What should ...
0
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1answer
142 views
How many worlds are there during branching in the many worlds interpretation?
Background and Question
"Measurements are modelled as interactions between subsystems of the universe and manifest themselves as a branching of the universal state." - Wikipedia
What is the ...
0
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0answers
36 views
How did people estimate the speed of light before modern technology? [duplicate]
I just read a wikipedia page on the speed of light. Apparently people have made pretty accurate estimates for almost 200 years. How did they do this? How did they measure any fundamental constant ...
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1answer
113 views
The problem of measurement in general relativity
I am looking for a good selection of articles and books on the topic of measurements in general relativity. The only one I'm really aware of is Reichenbach's "The Philosophy of Space and Time", which ...
0
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1answer
41 views
Does the length of wire affect?
I find the voltage of electric wire in between point 1 and point 2. I want to know if I use the differrent wire,long one and short one,the voltage will be equal or not?
0
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1answer
56 views
Strange anomaly in the calculation of the cosmological constant
I was trying to calculate the cosmological constant with two different methods proposed on the internet, that are apparently equivalent but they give different results and different dimensional ...
0
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3answers
168 views
Why nature rejects 100% accuracy in experiments? [closed]
I have never heard about any experiment performed which is 100% accurate (Sorry,if there is any).By the term accurate I mean accurate measurements involved in the experiment.Is it every time that an ...
1
vote
1answer
38 views
Measurement of Changes in the Weight of a Heavy Object
I am searching for an elegant way to measure small changes in the weight of a heavy object (a potted tree) over the period of one year.
However, I do not need to know the exact weight of the heavy ...
0
votes
2answers
54 views
Entropy of measurements; is the Von Neumann entropy lying?
Pre-measurement
Let $\left| \psi \right>$ be a pure state:
$$
\left| \psi \right> = a \left| 0 \right> + b \left| 1 \right>
$$
The density matrix of $\left| \psi \right>$ is:
$$
\...
-1
votes
1answer
44 views
How to locate where a ball hits the ground? [closed]
I want to locate a small ball when it hits the ground before it rolls or bounces. Consider a robotic gun fires a plastic pebble at an angle like artillery. The ball flies in the air about 0.5 seconds ...
0
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1answer
37 views
Visualizing Uncertainties
I am making an uncertainty exercise from a simple Physics experiment based on deriving the equivalent spring constant for a series combination of springs. The mathematical model for the combination of ...
0
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1answer
60 views
Why Does a Resistor's Resistance Vary?
Whenever we try to measure the resistance in a multimeter, the value is not the same for all measurements. Slight variations are observed over several measurements. But why this happens? And can this ...
2
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0answers
53 views
What caused the first measurement to the universe?
I've been bumbling with a question recently. People postulate that with the give model of big ban, particles forms and breaks and eventually became what we saw as of today.
However, if we put ...
1
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1answer
63 views
How to decide the number of significant figures? [closed]
When we do calculations involving significant figures with their uncertainties, Which rule/rules do we use to decide the number of significant figures in the result?
0
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0answers
14 views
How relative positions of battery and galvanometer affect the sensitivity of a wheatstone bridge?
I know one of the factors that affect the sensitivity of the galvanometer is the relative magnitudes of the resistances in the four arms of the bridge. the bridge is most sensitive when all the four ...
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1answer
55 views
How to find the possible measurements of a quantum system? [closed]
A wave function of an infinite square well is given as
$$ \psi(x) = \frac{1}{\sqrt{5a}}\sin\left(\frac{\pi x}{a}\right) +\frac{2}{\sqrt{5a}}\sin\left(\frac{3\pi x}{a}\right),\quad x\in[0,a] $$
How do ...
0
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1answer
13 views
How should I calculated a constant based on a set of experimental values?
I was wondering about the following example: suppose I wish to determine the spring constant determined by swinging a mass to it's end. It is given by the following formula:
$$T=2\pi \sqrt\frac{M}{k}$...
0
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0answers
13 views
Measuring inner choke point on non-uniform silica capillary tube
I hope this is an appropriate place to be asking questions like these (google brought me here when I was searching for a solution)! I make an assembly where a small silica capillary tube (OD of 1mm) ...
0
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1answer
43 views
Why do we subtract least count in measurement? Trying to understand intuitively
With respect to the following situation, it is quite clear that our true reading has to be at least 21degC. It can be more than that such as 21.4, 21.5. 21.7 etc. We can also see that the maximum ...
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6answers
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What is the most precise physical measurement ever performed?
Obviously some things, such as the speed of light in a vacuum, are defined to be a precise value. The kilogram was recently defined to have a specific value by fixing Plank's constant to $6.62607015\...
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5answers
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Has the speed of light ever been measured in vacuum?
According to: https://en.wikipedia.org/wiki/Cosmic_microwave_background the CMB (Cosmic Microwave Background) "is faint cosmic background radiation filling all space"
Also, https://en.wikipedia.org/...
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Does all measured quantities by Hamiltonian operator should be real valued? [duplicate]
am not familiar with QM , and i have checked web many times to know wether all measured Quantities of any arbitray system should be real since it is Hermitian ?
0
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2answers
51 views
What does it means to increase the accuracy of a screw gauge? And if so how to increase it?
This question is related to the following question from NCERT:
A screw gauge has a pitch of 1.0 mm and 200 divisions on the circular scale. Do you think it is possible to increase the accuracy of ...
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3answers
58 views
How can multimeter measure frequency with only one wire connected?
Many multimeters have the ability to measure Frequency along with AC Voltage, DC Voltage, Capacitance, Resistance ...
But how do they measure Frequency?
In my country, $50\ \text{Hz}$ is used as AC ...
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0answers
29 views
Different Quantum Measurements
What is the difference between an interaction-free measurement, a weak measurement and a counterfactual measurement in quantum mechanics?
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1answer
35 views
Adding or subtracting mean absolute error
In an experiment to find the length of a rod, n observations were made. ${a_1,\;a_2,\;.\;.\;.\;a_n}$. The mean (${a_{mean}}$) of those observations will give a value very close to the true length of ...
0
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1answer
29 views
Measuring small changes in length using the micrometer screw gauge
Which of the following method/instrument cannot be used to measure small changes of the order of a millimeter occurring in a length of about 50cm.
1)spherometer
2)travelling microscope
3)meter ...
