The Stroboscope And How It Works - F-J's Physics - Video 126
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- Опубликовано: 11 сен 2024
- WARNING: CONTAINS FLASHING LIGHT IMAGES. Here we look at the stroboscope, its uses and dangers. A chance to understand why wheels sometimes appear to go backwards on some films too. (Note that: The highest frequency of flashes of light that 'freezes' the rotating object is the rotational frequency of the that object. If you think about it, lower frequencies will do the same but the object might, for example, be rotating twice for each flash!)
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Very many thanks, F-J
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Very many thanks, F-J
I remember a certain party I went to and they were messing with the ceiling fan and a strobe light. It was the kind of party that made this the most phenomenal thing you ever saw.
Thanks Bryan - it is clear that you too have that wonderful knack of seeing how physics is all round us and leads to some really interesting effects. I probably would have bored everyone by pointing exactly that out but you are right - a great effect - what if the vanes were fluorescent and you had a 'black light on too!
Very educational Professor. Keep 'em coming 👌👍
Great, glad you liked it! Plenty more to come so thanks for supporting the channel again!
Excellent video and perfect timing. I was trying to explain how a timing light can be used to set ignition timing of most internal combustion engine. You explained it way better than I did!! Thanks for the video.
Thanks, that's very kind of you. And, yes, what a brilliant application, ignition timing. Not many people left who would understand that or know what a distributor was. Hated the risk of getting a shock or being caught in the fan belt on my Jeep! Thanks for watching and your kind comments! ruclips.net/video/9FoJjhdQjiI/видео.html
This video explains it very clearly. It helps me understand.
Excellent! So pleased it helped and good luck with your studies!
The most likely reason that wagon wheels turn backward in old movies is editing matches the old projection or camera frame rate with the current frame rate. The process is pretty simple. Just make an array of how different every frame is from its neighbor. This index should give you a starting place to choose images to duplicate or decimate. The sum of two pages xored together pixel by pixel is where I would start. I believe that can be scripted in ImageJ. The difference may also work. I chose XOR because it's uniformly fast(1 machine cycle) on all platforms.
A strobe light is great for timing and calibrating things for time. All you need is a ruler, a weight, and a way to drop the weight so it appears in the picture along with the subject illuminated by the strobe twice. A falling weight in front of a ruler allows anyone to calculate time inerval in a RUclips video. We used them for almost everything. If its an old one it may have an external trigger that can be set up to catch events such as gunshots.
Gordon, thanks very much for this excellent explanation. I do like the falling weight idea rather than the rotating disc type time stamping method. A bit of maths needed as it is non-linear of course but nothing suvat would not sort! Would make a good question for my A level students! Thanks for watching and taking the time to comment so fully.
The first time I heard about the danger to someone caused by a flashing (red) light was in the movie "The Andromeda Strain".
Yes, interesting Gregg. I believe they actually made the flash frequency incorrect purposefully so as to not induce any epileptic effects in viewers, though, in fact, the range of frequencies that cause issues are quite broad I am told and not restricted to one particular frequency of light flash.
@AnthonyFrancisJones Years ago, I was riding a bicycle going from Perpignan to Sainte Esteve France when I passed some evenly spaced trees on the right that blocked the Sun. My eyes had trouble shifting back and forth.
Yes, I have seen similar things on the motorway when there are regular barriers set up with the other headlights. There is a wall in one of the rooms that I work in that has horizontal wooden strips about 4cm apart all the way around it and I just cannot look at it without feeling dizzy! By the way I must do a Moire Fringes video at some stage too.
Fantastic explanation, but u could have used a little more technical terms
Thanks Muhammad. Is there anything more technical that you would like me to explain or to add? If so I can add it to the pinned comments. I made this video as a general science example so it was not meant to be too technical but I get your point - there is so much more one can say about strobes and strobing effects! Thanks for watching and taking the time to comment.
@@AnthonyFrancisJones How rotational speed of the fan can be matched with the frequency of light, by determining the amount of time the fan rotates to it's position and having that frequency in the light etc, overral a little more depth on technical side.
@@MuhammadAnas_Official Thanks, that's a good idea and would allow for the introduction to angular velocity ideas. I could do the experiment with a swinging pendulum too to show the similarities of linear (small amplitude) oscillations to circular motion. I guess I only have under an hour in my lunch break and no script so they are a bit quick and simplified but I do really value your input. It is always great to get suggestions even for other videos such as the Tennis Racket Effect or the Halbach Effect which were both suggested by different subscribers. There is so much interesting physics out there!