Funny thing is you helped come to that conclusion by not opening the faucet all the way. Depending on other factors it might be different. It’s that complexity that keeps me asking questions.
While we practically cannot speed up light, most of us aren’t measuring speed. We’re observing volume in full or in part. Blocking the beam by redirection to change the locally observed volume is exactly the point of the thread. Sometimes an analogy is useful, if not exact.
Quality isn’t the best because it’s a soft (flexible) lens and I just moved it with my hands. I left ambient light on to reduce brightness adjustments in my camera (compact camera, no manual settings)
However you see that it is indeed similar to a zoom light as there’s a position where LED and reflector are projected onto the wall. Near that position however there’s a position where that image is blurred into a quite good and quite bright spot.
Fresnel lenses are quite lossy, quite dome of the light is scattered at the edges. A real lens of same size would give a better performance, pot probably some more artifacts, too. Main contribution to throw is lens size and quality.
A high quality aspheric lens with same area and with a (bare) LED in it’s focus will have the best throw, but a smaller spot.
yeah, that was the base of my experiment, now i’m trying to move into adding combination of different lenses to see if i can manipulate lights into thrower or floodier ( for bike light)
i want to buil something like light device but in smaller scale
maybe you can give me some input on these experiement, i found a success hooking my Trustfire WF 502B into telescope and it able to throw as far as 300’+, but the hotspot starting to dissappear and turn into a doughnut … but it still reach
now… if i can somewhat miniaturize this device using combination of telescope optics ( which i have plenty of) that will be great
Only if you put the LED at the exact point your eye would be. At least on my spotting scope that’s how it works. Ironically this “throw” works better with an XM-L (being closer to the exit pupil size), at least with mine. Try it through a rifle scope…
And yes, works quite well to put a very bright spot on something a long way away.
Now if I could line the barrel of it with reflective foil like the OP……. :glasses:
using binoculars won’t work too well, as they have 2 lenses spread far apart, the telescope experiment was using 2 lenses but they’re very close to each other :). if you using freshnel lens (magnifying glass) you will see the result similar to mine
Strange… Mine makes a tight, sharp-edged, white dot, which gradually gets bigger until I run out of room. My whole yard only lets me “throw” about 100’. And 13 seconds later I’ve wiggled my hand and it’s over. When the rain & cold let up, I’ll see if I can put this mess together outside somewhere…
And I have no idea what the “math” subtext is all about. I’m sorry I let it slip into my quote.
(PS: you must be very calm, if you can use 15x binoculars effectively!)
I think it’s safe to assume he just used one lens set.
Of course, the 15x, while huge in binoculars, is just starting to touch most home telescopes’ power range. It seems the magnification should matter…
Speaking of which (and I note even you don’t mention the reflective foil anymore, which was all I could see of your apparatus until I read the thread) has anyone here ever looked at a Lighthouse? (yes, ma_sha1’s beamshots always make me think of them) They’ve been using Fresnel lenses for a long time. Maybe there’s some useful knowledge there? (especially if your aspheric sticks out & gets banged up)
HAPPY NEW YEAR!! (I noticed your post time.) :party:
But wait… Did you notice the gobs and buckets of waste light billowing out of your apparatus??
I though you wrapped it in reflective foil…
That’s what I get for thinking.
And I’m half asleep already. I love the idea, the quick wit, and the clever effort. I especially love the way you defend your ideas. Nicely done (ditto for the rest of you, scaru, ma_sha1, and everyone else!! THANK YOU ALL!!!) (sorry I can’t remember all the names at 02:30) Now I’m going to go pull up the Michaelson-Morley experiment again & read myself to sleep…
i only covered the front part of the tube…the waste light? you meant that “ring” light? it coming out from the edge of the device
i’m glad you find this reading amusing ,perhaps it will help lull you to sleep
AND a clever way to stir up a Very Useful discourse.
That depends. Have you seen a Fresnel with an aspheric profile ? I don’t know, but knowing how Fresnels are made, it seems only a matter of asking. There are many lighthouses which wouldn’t be there were it not for M. Fresnel. How many aspherics protrude enough to be a problem?
I wasn’t going to post anymore either, but this is too much:
(Since no one here wrote this, I see no reason to hold back with the cattle prod)
Or STOP, as any child who has tried this will tell you. This is why we tell physics students to go outside and play.
“Accumulate”?? As in “compress”?? How does a physics student compress or accumulate water? H2O is pretty hard to compress, IIRC. All that’s left is “flow out of the hose”, which makes “either” somewhat pretentious. And this guy’s considered an “expert”? Remember, “EX” is “FORMER” and a “SPURT” is a “DRIP UNDER PRESSURE”…
Uh… Only in a college physics classroom. Out here in the big room with the blue ceiling, our hoses expand considerably (being flexible and all) and will most definitely increase the pressure when you relax your finger enough (or open the spray head) to allow the flow to resume.
Or NOT. “Has to”?? Says WHO? And how did he propose that the same flow rate at the same pressure makes it through a smaller opening??
People, drugs don’t do this. Only a long period of faith-based indoctrination can lead to this sort of “Bovine Scatology”. And you wonder why Light is so hard to understand!
But speaking of drips, it’s really a shame that light does not follow the rules of ‘textbook fluid mechanics’. Then we wouldn’t have to fight through the whole Double-Slit quagmire; but that would also render this thread moot. Even in electronics, we get past the “water” metaphor as quickly as possible, to limit (or “restrict”) confusion (hint, hint).
I’m sorry, it’s too late and I’m too interested in the rest of this thread to give this “physics grad student” opinion the treatment it deserves. To prove it to yourself, take a deep container and poke a few holes in a line up-&-down. Cover them & fill it with water. Uncover all holes. Which one squirts farther? Why? Now put a nozzle on your hose & seal it. Open the spigot fully & tell me how much water comes out. Why? If you can afford it, put a pressure gauge on your hose and observe. (And if your kid wants to go to Berkeley physics, send him to the Army first so he can learn something useful.)
Speaking of reasoning by analogy, should I use a thrower or a flooder to see this Darkness on the back of my eyelids?
(Sorry if I gored your sacred cow. It’s a Dimbo thing, and I’m not usually THIS nice, this late…)