# Tag Info

32

The LIGO beam is 200 W as generated at the input mode cleaner; the beam is then recycled multiple times in the arms, increasing the power density significantly. This requires large optics with near perfect coatings in order to avoid "hot spot/cold spot" damage from various types of possible defects. But there is an additional reason for the large beam size, ...

13

This must have been a conscious design consideration, since it means that a much larger volume of vacuum must be maintained While I don't think that it's what motivated LIGO, the volume is not as much a consideration in high-vacuum as the surface area. Once the chamber has been pumped out, the ultimate vacuum level is set by the rate of ...

7

It's true that if you know the masses of, e.g. two orbiting stars $M_1$ and $M_2$, their orbital period $T$, and the distance $d$ between them, then you know $G$. And we can measure $T$ pretty well and $d$ fairly well. But how do you think we figure out the masses of the stars? We can't just count the amount of stuff in them; we have to infer the mass from ...

7

My bet is that your fiber is very short (something like one meter or so) and that the fluctuations you see on the output mode are due to cladding modes, i.e. a part of the injected light propagating into the cladding of the fiber instead of the core. The resulting fluctuations are due to external perturbations of the fiber (thermal fluctuations or you ...

4

This sounds as though the aberration in the laser's output could be fluctuating owing to "mode hopping" (where several of the laser's cavity modes are active and playing a time varying role) so that, even at a constant output power, the aberration of the output beam varies with time. Wavefront aberration is roughly the Fourier-dual of Strehl ratio. This ...

4

I did a couple of experiments with a DSLR and a cheap red home improvement laser level. The most revealing factor is that a direct reflection of the laser on the CCD sensor gives a distinct square diffraction pattern. This is pretty much what one would expect from a camera that has square pixels. The reflections have sharp peaks that are spaced fairly far ...

3

Some additional reasons not mentioned in the other answers: Clipping losses: Gaussian beams fall off exponentially, so any finite size tube will cause a small loss in power. Typical design rules when making an optical design of such instruments is that not more than 1 part per million of the light is lost due to the finite size mirrors. Typically, all ...

3

The basis for constructing a working ice house is described in The First Icehouse in America? The fundamentals are: a large mass of ice; good drainage, an environment with constant temperature. Insulation of the ice with saw dust or straw helps to slow the melting, but it must be kept dry, which requires good drainage. You would obtain a better discussion ...

3

The experiment certainly does produce a very general complex superposition of momentum eigenstates. The spread is not "small" in any way – virtually all allowed (by conservation laws etc.) final states are represented in the superposition for any initial state. We detect particles of particular momenta in the final states because the detectors (e.g. at the ...

2

Yes the human body has a gravitational field, and yes it's large enough to be measured experimentally (see the Cavendish experiment).

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Some other effects that might be at play: 1. Reflections from the end-faces of the fiber causing interference 2. Brillion Scattering 3. Check to see if in fact the fiber you're using has a cut-off wavelength shorter than the wavelength you're actually using.

2

Observation of a single electron in a Penning trap shows the upper limit of the particle's radius is 10^−22 meters Reference.

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Comparison of fabrication techniques for hollow retroreflectors describes, in great detail, the two obvious methods: The use of a precision solid prism corner cube as a mandrel to hold the glass plates prior to gluing of the edges. An adjustable set of precision mirror mounts, designed to hold the three plates In both cases interferometric techniques ...

2

The direction of the force due to surface tension depends on whether the liquid wets the the body or not. In the first picture liquid does not wet the body, so the force is directed in such a way as to decrease the contact surface area of the body with the liquid. That is, upwards. In the second picture liquid wets the body, so the force is directed in ...

2

During the acceleration phase the object's movement can be modeled with the quadratic curve $$x=x_0 + v_0t+\frac{1}{2}at^2 \qquad\text{where } x_0 \text{ is the initial position, and }v_0 \text{ is the initial velocity}$$ During the constant velocity phase, the object's movement can be modeled with the linear equation $$x=x_1 + v_1(t-t_1)$$ where $x_1$, ...

2

In the Geiger region an incoming charged particle produces an avalanche of charged particles which migrate across the tube and produce an easily measurable electric pulse on the electrodes. The tube contains a halogen quenching agent which then stops the production of further charges so that one incoming particle produces one pulse. As the voltage across the ...

2

It seems like some kind of Newton rings formed. Does your mobile camera has a flat thin sheet covering the lense. If so, the newton rings formed is captured in the sensor. Having said that, I can't explain why there are multiple of them, that too in a lattice formation. May be if the distance between the thin sheet and lense increases we have various newton ...

2

This article appeared in Mother Earth News in olden days (1972!) and discusses ways to build an ice house for cool storage and how to harvest the ice with which to fill the house once its completed: How to Build an Ice House Of course, ice houses work better in some areas due to the local climate. An ice house would be a worthwhile project in Vermont, ...

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One indication whether the 'inner' balloons are filled with helium or something heavier is whether the 'outer' balloon still floats in air or not. Whether it floats or not depends on whether its overall density is lower than air's density or not. Its overall density $d$ is simply given by: $$d=\frac{\Sigma m}{V}$$ Where $\Sigma m$ is the sum of all the ...

1

The small number of "conceptually independent types of processes and calculations" is exactly a symptom of the theory's being fundamental! Even in classical physics, all calculations could have been mathematically reduced to the calculation of the final state that evolves from an initial state (or a state that is stationary etc.). In quantum mechanics, this ...

1

Young's modulus of a material doesn't depend on geometry. It is a mechanical property of material and depend on its structure. But, we cannot determine Young's modulus of a material by its structural properties experimentally. We (in your case) want to determine $E$ (Young's modulus) by using $E=\large{\frac{PL}{A\delta}}$ in a tension test ($P$ is the ...

1

There is some misunderstanding here. whether a freely falling charge radiate photons, how strongly and relative to which frame of reference it does or does not radiate if you mean a charge in free fall. In this calculation:, from the conclusion It is found that the "naive" conclusion from the principle of equivalence - that a freely falling ...

1

It is done all the time in acoustics, ask any musician! However Shen probably was referring to harmonic generation in radio frequencies; with radio is is called a frequency multiplier. The heterodyne technique was invented in 1901. The Kerr effect was first found about 1876. The first footnote in this article provides some historical background: altering ...

1

Let us dive into the light clock thought experiment, Special relativity is based on two postulates, There is no such thing as absolute motion. Phrased another way, all laws of physics should be invariant under changes in inertial frame. The speed of light is measured to be the same value in all inertial reference frames. Let's say you are on the train ...

1

In essence you are trying to decide whether the friction forve is proportional to the velocity or velocity squared. Assume that the period of a swing $T$ stays constant. If $x(t)=A_oe^{-\gamma t}$ then if after $n$ swings the amplitude is $A_n$ $A_n = A_o e^{-\gamma T n} \Rightarrow \ln A_n = -\gamma T n + \ln A_o$, so plot a graph of $\ln A_n$ against ...

1

If your curve-fitting program allows it, instead of fitting $y=a+bt+ct^2+dt^3$ you could try fitting $y=d(t-a)(t-b)(t-c)$. The output parameters $a$, $b$, $c$ will then be the required roots and the errors (or rather variances and/or co-variances) will be included in the statistics.

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Judging by your Q1, I think you are asking about error bars for data points in graphs, especially in relation to plotting a line or curve of best fit. Error bars are not often calculated statistically for this purpose. To do so, a sample of N measurements must be made for each chosen value of the independent variable x and a mean and SD calculated. The ...

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It depends on the efficiency of the RO membrane. When the membrane conversion rate was below 20 percent, the answer in general would be yes. However, with the newer type membranes the conversion rates are quite high. In RO sea water desalinization, the normal pressure required to force the the pure water molecules through the membrane is in the range of ...

1

There are often several different methods of synthesizing materials, and in lots of cases they arrive at the same result. Sometimes the experiments you want to do will depend on your growth method, though: for instance, the polycrystalline samples you get from solid state reactions can be good for x-ray or neutron diffraction studies. If you want to ...

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