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  1. sophiecentaur

    B Poisson spot madness

    I see where you're going with this. But, unlike a spherical lens in which can be a high level of what is referred to as spherical distortion, for a solid disc or sphere there is a massive range of distances where you get some form of 'focus'. Right in close there is a shadow and at a great...
  2. sophiecentaur

    Insights Fundamentals of the Diffraction Grating Spectrometer - Comments

    Frequency measurement and resolution at RF will take you easily to One part in 1011. Pretty damn good eh?
  3. sophiecentaur

    B blocking all type of energies/waves/signals

    Even gamma rays will penetrate lead if it's not thick enough. Longer wavelengths will cause finite currents to flow in the sides of a metal box and that can cause radiation to the inside. The answer to your question depends upon the particular frequency you are interested in and just how much...
  4. sophiecentaur

    B Poisson spot madness

    I'm trying to make some sense of this. How can a coin resemble a lens? Also, what is it that looks like a "parabolic mirror"? A diagram might have helped. Remember, PF is not psychic and we can only react to what is posted. What's actually going on in those images? The Poisson Spot is what can...
  5. sophiecentaur

    I Mirror phenomenon

    At night, a bright, localised source will form a point image on the retina that is intense. In human eyes, this intense spot will be bright red (blood colour) and the eye lens will focus this image at 'infinity' in the direction of the original source (reciprocal optics). That accounts for...
  6. sophiecentaur

    I Why is the output current of a transformer fixed?

    We need a response from @pkc111 before we can progress this. He / she feels that The R=V/I should fit in somewhere but you have to use the correct R in each of the circuits. An additional concept that may or may not help is to point out that, if the transmission line is supplying 150kW at 10kV...
  7. sophiecentaur

    B Electromagnetic radiation measurements

    Could you be a bit more specific about your interest in this? Do you need to assess the level of exposure under a particular circumstance? As @tech99 says, there is a lot of witchcraft in this topic. The human body is affected differently in different situations, according to the surroundings...
  8. sophiecentaur

    I Why is the output current of a transformer fixed?

    I don't quite know where you are coming from here. The secondary winding is a source of induced emf. It's the Load Resistance that governs the secondary current (include the extra 2 Ohms if you want to). If you short out the secondary then that's not a mode that most transformers are happy with.
  9. sophiecentaur

    I TE and TM modes in optical fibers

    It strikes me that a bit of basic reading about conventional waveguides could help you get into this subject. Waveguides are very often rectangular section (hard to make optical fibres this shape) and the analysis is much more straightforward. Piling in with the necessary Bessel functions for...
  10. sophiecentaur

    B Trying to make an electromagnetic shaker device

    If you want to shake something at a variable and controllable rate then a variable speed DC motor with an eccentric weight on the shaft will satisfy many requirements. Crude but very effective and will work at a range of powers. 500W Brushless motors are available for small machine tools and...
  11. sophiecentaur

    I Why is the output current of a transformer fixed?

    For resistive loads, it's exactly the same. RMS Volts and Current are always assumed unless told otherwise. First pass through the solution for a transformer doesn't need to consider Inductance - just the basic Transformer equation. There's no need to make things any more difficult until you...
  12. sophiecentaur

    I Interference intensity

    It's multiplicative in the ideal case. The element pattern and the array pattern can be multiplied as long as the elements are all identical and pointed in the same direction. In reality, the distribution over each slit may be a bit different etc. etc. There are layers upon layers of...
  13. sophiecentaur

    I Interference intensity

    Where does your "infinity" come from? I think that could be the root of your confusion. Slits, by definition, are all directional. For simplicity, think in terms of two omnidirectional (in XY plane) ideal radio antennae and the maxima will all have the same amplitude. The trig functions in the...
  14. sophiecentaur

    What is the Sun's energy content at the equator?

    You are right to question some sloppy terminology. Bear in mind that the Earth's orbit round the Sun is not an exact circle. That means, despite any tilt or atmospheric factors, it can't be a 'constant'. It's a bad idea to get too hung up on 'words' when experimental evidence challenges them.
  15. sophiecentaur

    Help with Building a Vacuum Chamber

    I've been looking at temperature / partial pressure tables and I can't come to a conclusion about what would be best value. Where did your 1 psi figure come from? Experiments? The latent heat could perhaps be involved?
  16. sophiecentaur

    Help with Building a Vacuum Chamber

    Good job!! What pressure did it operate at? What kind of pump did you use?
  17. sophiecentaur

    Help with Building a Vacuum Chamber

    Kiln dried wood is not as good as naturally seasoned wood. I remember seeing images of a tree trunk, sawn into planks and then re- assembled with small air spaces left between the parts. Natural drying out that way is the best way to avoid stresses and consequent warping. But, if it's firewood...
  18. sophiecentaur

    I Studying the air layer over a solid object

    How thick is the interface layer of interest? Is there some sort of gradient of temperature or gas concentration? AS @jrmichler says - we need to know more about this.
  19. sophiecentaur

    Convert Lux to RGB

    Having looked at the data sheet I am a bit clearer about what the device does. It will give you RGB values for a particular displayed colour according to (or near) the formula in the link higher up. Afaics, you want to know the RGB values needed to produce a specified colour on the scree in...
  20. sophiecentaur

    Convert Lux to RGB

    It depends on what you want to achieve. Do you want to produce 'four colour images' with a three colour display' to include IR? I am still not clear which voltage you refer to as the device appears to produce four digital (8 bit Edit - 16bit) output signals.
  21. sophiecentaur

    Convert Lux to RGB

    Yes. It does its best to achieve that for an 'average' observer. I think including a nonlinear factor would not be possible - can you think of how it could be? You need to read more deeply into what is meant by luminosity. The eye is adaptive so how could you chase that? The block diagram...
  22. sophiecentaur

    Radio bands

    Ah well, that's it!! Who is the intended audience for these posts? Which of us is always thinking carefully? (Present company excepted of course) The term "CW" means two different things, according to context. If you say you picked up a CW signal, that does not imply that some old geyser was...
  23. sophiecentaur

    Convert Lux to RGB

    I'm not sure that the above link tells the whole story. It may relate to a particular piece of equipment. I would imagine the gains in the four channels of your equipment should take care of things, largely. Your PC will do the usual thing for displaying RGB signals. (0 - 255) RGB analogue...
  24. sophiecentaur

    Radio bands

    Imagine you made a receiver for 'CW comms' with a very narrow band receive filter, (Bandwidth of 0.01Hz). If it were tuned spot on the carrier frequency, you would just see the carrier with no visible envelope. That's despite the fact that the carrier "isn't there" for half the time; the filter...
  25. sophiecentaur

    Help with Building a Vacuum Chamber

    The ‘problem’ with vacua is that even moderately low pressure involves large Forces. A guy who supplies me with logs told me that it’s common to use old shipping containers with a fire of burning logs beneath. (A ready fuel source). Cycles of heating and rapid air extraction gives good drying...
  26. sophiecentaur

    Radio bands

    CW is an oxymoron. The wave isn’t continuous when Morse keyed so where is the difference between that, AM and all other forms of mod? Your post could easily Be taken to imply some hard boundary between modulation and non-modulation. Arbitrary exceptions can confuse.
  27. sophiecentaur

    Help with Building a Vacuum Chamber

    I was thinking of an offcut of Oil / Natural Gas Pipeline. It would take a lot of dry timber to pay for itself, judging from those Google Images.
  28. sophiecentaur

    Help with Building a Vacuum Chamber

    If you want a strong enough structure to support a high vacuum then go for a cylinder with hemispherical ends and strong flanged joints. That's inherently self supporting and it's pretty universal (see submarine hulls!) But, to the basics: what actual pressure do you reckon you need to speed...
  29. sophiecentaur

    Radio bands

    We have got to the stage of definitions and classifications which is always a dead end. We both know what's what, here, I think. People tend to over estimate the importance of a 'carrier'. I would say that the only mod system that has an actual carrier is AM or its near derivatives. In that...
  30. sophiecentaur

    Radio bands

    Not really . To 'carry information' it has to be modulated, which means it is no longer a single frequency. Splitting hairs, perhaps but the information has to be spread over a finite bandwidth (the channel). In AM and some other systems, there is a carrier present at all times. No modern system...
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