# Tagged Questions

The result of sampling the property of a system

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### Radius of $n^\rm{th}$ orbit of an atom in terms of Bohr's Radius

Bohr's Radius$=0.529$ Angstroms My book says that the radius of $nth$ orbit of any atom can be calculated by: $$r=n^2 a_o$$ where $a_o$ is Bohr's Radius. But I think it should be given by following ...
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### How to find the error of all the counts within the Full Width Half Maximum (FWHM)?

We've been doing Gamma ray spectroscopy and have peaks from various sources. We'd use Poisson statistics, but obviously the detector doesn't have a resolution of zero, thus we are summing the counts ...
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### Could neutrinos be used to take high resolution pictures of atomic nuclei?

Of course, this is obviously not feasible with modern technology but is it theoretically possible?
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### Practicality of measuring observables

In quantum mechanics Hermitian operators acting on the Hilbert space of a system are observables. From what I understand this means that there is some measurement we can do such that the eigenvalues ...
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### How well can we localize gravitational wave sources?

A recent question cited a story about the recent gravitational wave detection saying that we can use the gravitational wave sensing to find supernova earlier in their process of collapse: [with ...
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### How to (safely) measure the surface area of a human body? [closed]

Here's a question just for curiosity. You measure mass on scales. You could measure volume by submerging in a bath with a snorkel system. But how could you measure a living human's surface area ...
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### How could the BOE (barrel of oil equivalent) be measured?

The barrel of oil equivalent was given as an example of gigajoule scale energy. "The barrel of oil equivalent (BOE) is a unit of energy based on the approximate energy released by burning one barrel (...
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### Calculate how many photons hitting a sample that are absorbed

In the determination of the quantum yield of a photoisomerization, $\Phi,$ the following is needed $$\Phi = \frac{\mbox{Number of "reactions"}}{\mbox{Number of absorbed photons}}$$ The photon flux ...
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### Venturi “Turn Down” [closed]

I'm sorry if this isn't the right forum for this question, but physics is the only stackexchange which had many results for Venturi. I'm trying to measure the flow of air through a 16mm hose/pipe ...
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### Is there any well-defined, measurable atomic size?

Is there any well-defined, measurable size at the atomic scale? I was under the impression that the van der Waals radius was a good way of describing the size of an atom, but it turns out to be a ...
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### Is there a tool to measure the chemical potential of a system?

Let's suppose I put you inside a room filled with a gas. You can measure its pressure directly with a barometer. You can measure its temperature directly with a thermometer. Can you measure its ...
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### How precisely do we know the van der Waals radius of hydrogen?

I've found several sources that say the van der Waals radius of hydrogen is $120 pm$. How precisely do we know this number? What order of magnitude is the error on this measurement?
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### Position from acceleration, or acceleration from position, to track an object moving the speed of sound

I'm working on a project that involves tracing the motion of a fast-moving object (approx the speed of sound) through a fairly defined trajectory. Would it be more accurate to measure the position of ...
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### Photo Multiplier Tube Usage

How is it determined that a PMT measures only one photon ? By the energy that one photon is supposed to have ?
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### Is it possible to determine when an accelerometer is in a vibrating state compared to a non-vibrating state?

I would like to know if so, how raw 3-axis accelerometer data could be analyzed and manipulated real-time to register periods of vibration. The device being used has a max sample rate of 62Hz (I ...
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### measuring average directional intensity of LED?

Although I am poor at physics and math I want to compare two light sources of which I haven’t decided the specific brand yet. I was thinking of florescence bulbs versus LED lamps. So something like ...
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### Does measurement really affect polarization?

The answer must be yes but I have trouble dealing with the explanation given here. As you can see the light is polarized at an angle theta to x axis. After it passes the polarizer A which is along x ...
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### How to practically measure the heat capacity of a large object besides bomb calorimetry?

I need a practical solution to non-destructively measure the heat capacity of a variety of large objects containing many materials and having complex geometry which includes internal hollow areas. ...
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### Given a dimension of a known object in the image, how can we calculate the dimension of other objects in the same image ?

The question considers a very specific scenario in which we have an image with let us say, two rectangle objects. We know width and height of one object. How can we calculate the dimensions of the ...