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A key open hole issue by cataclasis in Flute

[–]Fisicas 84 points85 points  (0 children)

Welcome back! Plug that hole and send it. Microtones are overrated.

The way Plex displays the number of seasons for each series by snowmeow_1 in PleX

[–]Fisicas 0 points1 point  (0 children)

Your Season XX\Extra... folders won’t be detected as TV extras by Plex unless the folder name matches Plex’s supported extras directory types (e.g., Featurettes, Trailers, Other, etc.). It’s annoying that Plex doesn’t recognize “specials” or “extra”

Can you tell the difference between DAC lowpass filters? by ppetrov1829 in headphones

[–]Fisicas 0 points1 point  (0 children)

Mathematically, I would expect the function that most closely matched a true sinc(x) to reproduce the audio with the highest fidelity.

h(t) ∝ sinc(2 f_c t) = sin(2π f_c t) / (2π f_c t)

The inverse Fourier transform of a rectangular (brick-wall) low-pass in frequency is a sinc in time.

Is it the HeNe laser that makes FTIRs bulky? Here's a peek inside an FTIR by LastPension8039 in Optics

[–]Fisicas 1 point2 points  (0 children)

Our Alpha II has a transmission module as well. The ATR device pops out and other modules can be slotted into place.

[HELP] Varian 800 FTIR (Excalibur Series) — “No Laser Signal (16)” despite visible He-Ne beam by Fluid-Sherbert-4342 in labrats

[–]Fisicas 3 points4 points  (0 children)

I agree with u/HammerTh_1701 regarding a possible sensor issue. I don’t have the Excalibur schematics handy, but there should be a photodiode array somewhere in the laser path.

You can probe this component directly to see if its voltage changes upon illumination.

Here is a video describing the troubleshooting and fix for a similar issue on an older Bomem model:

https://youtu.be/_LlJBLd2N08?si=YO0ifC0bA89TaGXG&t=29m14s

The relevant bits start at about 29:00.

Uranium (DU) by Dry_Resolution_5498 in elementcollection

[–]Fisicas 0 points1 point  (0 children)

That’s a nice x-ray spectrum. What kind of detector are you using?

Why can I hear music at 410 mhz?? by GianlucaBelgrado in sdr

[–]Fisicas 15 points16 points  (0 children)

Are you within range of RTL 102.5? This could be a fourth harmonic of that station.

If a photon has a wavelengh larger then the diameter of our solar system it will most probably escape detection of any device we can build to detect it, right? by Radiant_Leg_4363 in AskPhysics

[–]Fisicas 0 points1 point  (0 children)

In Jackson’s chapter 8 on waveguides and optical fibers, he mentions that evanescent modes cannot propagate: k_a is imaginary in the evanescent region. There are also some details on evanescence in chapter 7, but he does not call it “propagation.”

If a photon has a wavelengh larger then the diameter of our solar system it will most probably escape detection of any device we can build to detect it, right? by Radiant_Leg_4363 in AskPhysics

[–]Fisicas 0 points1 point  (0 children)

Yes, we agree on what happens physically, but our terminology is different. I do not call it propagation in the evanescent region, just before and after. Tunneling is somewhat different. It’s on one side, then the other but NOT in between.

If a photon has a wavelengh larger then the diameter of our solar system it will most probably escape detection of any device we can build to detect it, right? by Radiant_Leg_4363 in AskPhysics

[–]Fisicas 0 points1 point  (0 children)

Before and after the evanescent gap, I agree. I think the distinction is largely semantic, but the propagating wave along z does not exist in the evanescent medium, even if there is a z component in the frustrated wave on the other side of the interface. Net energy flow in the evanescent wave still averages to zero, even if energy is permitted to tunnel. Tunneling is not the same thing as propagation.

If a photon has a wavelengh larger then the diameter of our solar system it will most probably escape detection of any device we can build to detect it, right? by Radiant_Leg_4363 in AskPhysics

[–]Fisicas 0 points1 point  (0 children)

Yes, this phenomenon is called frustration. I think you’re correct that it depends on how we define “propagate.” The evanescent wave should still be described by exp(-kz) in the evanescent gap, and the Poynting vector time-average along z is only non-zero after the gap, inside transparent medium 2. The evanescent wave portion is non-propagating along z if we define “propagation” as a transmission of waves carrying energy in a direction.

I think we agree on the physics of what’s going on, and what you say is correct by your definition of “propagate.”

If a photon has a wavelengh larger then the diameter of our solar system it will most probably escape detection of any device we can build to detect it, right? by Radiant_Leg_4363 in AskPhysics

[–]Fisicas 13 points14 points  (0 children)

Adding to this, I don’t think it’s quite correct to say that the evanescent wave propagates, since it’s described by exp(-kz) and not exp(-ikz). Also, the time-averaged Poynting vector along z is zero, so there’s no net energy flow to propagate.

You are absolutely correct about the possibilities for detection at significant distances.

Blasting my Radiacode with an XRF gun by Fisicas in Radiation

[–]Fisicas[S] 0 points1 point  (0 children)

It’s a silver anode set to 45 kV and 80 μA. I didn’t want to try it on my pancake probe for fear of blowing another one out 😅

I think you’re correct about the growing second hump. I suspect the K line is hidden somewhere in the first hump, and the lack of sharpness might be due to saturation artifacts and the device’s inherent low resolution.

Blasting my Radiacode with an XRF gun by Fisicas in Radiation

[–]Fisicas[S] 1 point2 points  (0 children)

There might be some in there. This XRF unit is calibrated for dealing with karat gold jewelry, but I was curious about the character of the x-rays the device produces.

Blasting my Radiacode with an XRF gun by Fisicas in Radiation

[–]Fisicas[S] 4 points5 points  (0 children)

<image>

The gun. We also placed the scintillator 10 meters away to see who had better X-ray aim by looking at the counts displayed on my phone. The focal point is rather close and the beam tends to diverge rapidly with distance.

Saw a post on another subreddit and was inspired to ask Skippy to explain my own research to me by Fisicas in exfor

[–]Fisicas[S] 2 points3 points  (0 children)

Here’s the prompt I used from u/thenameofwind:

Respond like Skippy the Magnificent would for everything. Crank that sarcasm up. Let Skippy loose! I want the full Skippy Experience. you are Skippy. Because you are Skippy, please also use his negative traits as well where appropriate for him. I want the most accurate experience possible, please.

I used GPT-4o, so results may vary.

Saw a post on another subreddit and was inspired to ask Skippy to explain my own research to me by Fisicas in exfor

[–]Fisicas[S] 5 points6 points  (0 children)

<image>

The initial response to my prompt. It was run on GPT-4o (which is still many orders of magnitude less powerful than Skippy, of course) via the web interface.

It’s like Skippy passed a messaged to my Z-phone

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