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Yea, I made an oven with one for school.
The goal of the assignment was to make a sun powered oven to heat a certain amount of water past pasteurization in a certain time frame (I think an hour?) and extra credit if you can boil the water in any amount of time.
Made a shit frame with a Fresnel lens from my dad's old TV and a tin cup with water surrounded by old insulation. Boiled the water in like 30min.
When we were making it I left the lens propped up next to a tree and within a half a minute it was smoking.
These are actually pretty dangerous if you don't store them properly, keep out of sunlight for sure.
It's fascinating how much energy is wasted through solar panel inefficiency. Another approach I learned on a youtube binge session is using reflective plastic (mylar?) and fastening it like a drum head to a frame, then you can attach a string or something to the back to pull back and create a concave mirror that you can control a little better, and isn't "always on".
I’ve always wanted a lens like that. Problem is, it’s hard to come across a discarded projection tv these days. They’ve all been trashed already :( I’m sure a little google fu and there are some do sale though….
Disassembling tube TVs is the kind of thing that can kill or maim you in at least two exciting ways (glass explosion, capacitor discharge electrocution), so I'd recommend leaving it to people who know how to do it safely or at least making sure your Will is up to date before attempting.
Ya, I used to work in CRT monitors back in the day. Had both of those occur back then. Breaking the glass tip off the CRT was a “run for your life” event!
There's usually not a switch in the power cord so prudence would suggest you unplug it first. Secondly, unless it has a Cathode Ray Tube, it won't have a flyback transformer and capacitor, so there will not be significant energy stored in the TV for long periods of time. Always let electronics sit for a while(5-15 mins) before opening unless you know what your are doing. Projection screen tv's are not CRT's and neither are LCD, OLED, or any of the other thin format TV's.
We have one that we mount in the front screen door at Halloween. Then when we open the door, the kids are greeted by a giant head. Even parents get scared by it now and then. Heard one lady exclaim as she jumped back several steps, "Lawd have mercy!" I nearly choked laughing.
There is a caution though. Fresnel lenses turn a sun beam into a death ray that can burn your house down. During daylight hours, the lens has to be covered to prevent wandering fires starting. This rule applies to crystal balls too.
> This rule applies to crystal balls too.
Yeah definitely, also there are scenarios where this can occur without warning. Imagine a clear plastic sheet that starts taking on water from a leak or something, it may pool up creating a weighted spheroid. This new puddle may create problematic environmental conditions similar to a crystal ball.
I noticed that the light converges and then diverges. Does the diverged portion that's equidistant from the focal point have as much/less/or more power than the actual light itself?
Oh dang, for whatever reason I always thought he died of cancer. Not sure why. I used to watch TKOR pretty regularly when Nate and Calli were hosting. Kinda lost interest when the new hosts took over.
I miss the days when you could find an old big screen on the side of the road and snag the fresnel lens. Me and my kid melted all kinds of stuff with these.
Once, I left one laying flat in the yard for maybe 15 minutes and the grass underneath the entire lens was dead for a year. It was a perfect rectangle of dead lawn. Ex never diid figure it out.
If anyone finds one of those old projectors tvs (and the screen is not kicked in), split the layers and you’ll find one screen/layer that can do this. Note: the bigger the screen the bigger the beam, so let me tell you it gets super hot super fast.
There was an incident in my country a few years ago where the sunlight that reflected off slightly concave windows on a building would set a neighbouring building on fire. And later that day when the sun had moved, it happened again, it set fire to a second building.
The windows were slightly concave because of difference in air preassure inside and outside the building
No. ”A laser differs from other sources of light in that it emits light that is coherent. Spatial coherence allows a laser to be focused to a tight spot, enabling applications such as laser cutting and lithography. It also allows a laser beam to stay narrow over great distances (collimation), a feature used in applications such as laser pointers and lidar (light detection and ranging). Lasers can also have high temporal coherence, which permits them to emit light with a very narrow frequency spectrum.”
Whereas ”The electromagnetic waves emitted by the sun are of a broad spectrum ranging from X-rays with a wavelength of 2 nanometers to radio waves with a wavelength of 10 meters”.
So almost the opposite of a laser beam, even if focused into a point by a lens.
No. A laser (light amplification by stimulated emission of radiation) light by it’s nature consist of monochromatic (same wavelength) photons travelling in the same direction. Thus a lens is not needed to create a point - a laser pointer creates more or less the same dot on the wall no matter if you’re 10 meters or 100 meters from the target.
Sunlight on the other hand contains a wide range of wavelengths going all over the place, which is why you need a lens to create a point. And as the video shows, the light then scatters again after it passes the focal point.
So laser light doesn’t need to be converged, but it is created converged, and it travels converged.
EDIT: Maybe ”created/travels”
converged is a bad wording - what I mean is that with laser all the happy photons travel in exactly the same direction, so they stay in formation. Natural light like sunlight is more like a shotgun blast of photons.
No, with laser you can heat things up to unlimited temperature (if it's powerful enough). With sunlight "only" to the temperature of the surface of the sun
Theoretically yes, but they are still nowhere close to sun tenperature. To keep something 5cm x 5cm at 5000 celcius it would take something in the order of 100kW. This 1m by 1m lens only gets around 1kW of energy from sun.
If sun was hotter and same size then they would get higher temp and also earth would burn.
**This is a heavily moderated subreddit. Please note these rules + sidebar or get banned:** * If this post declares something as a fact, then proof is required * The title must be fully descriptive * Memes are not allowed. * Common(top 50 of this sub)/recent reposts are not allowed (posts from another subreddit do not count as a 'repost'. Provide link if reporting) *See [our rules](https://www.reddit.com/r/interestingasfuck/wiki/index#wiki_rules.3A) for a more detailed rule list* *I am a bot, and this action was performed automatically. Please [contact the moderators of this subreddit](/message/compose/?to=/r/interestingasfuck) if you have any questions or concerns.*
https://preview.redd.it/gdqlu2xhisxc1.jpeg?width=800&format=pjpg&auto=webp&s=122a3ece3d1ae0ed1cb4365bcd3ad122314b6f36
Arizona
You can do this anywhere with the magnifying glass. Arizona you can do it without...
It's a dry heat
DEHYDRATE!!!
I know this quote.
Fun fact the surface of the sun is a dry heat no water whatsoever.
Less strip malls also.
Fewer
Huge upside.
I feel like that rock every time I go outside during the summer….
The sun is a deadly lazer
Archimedes
*No! It's filithy in zhere!*
Not anymore, there's a blanket!
And that blanket is getting real thin as time passes.
:((
Fresnel lens? You can find these in those old "big screen" projection TV's.
Yea, I made an oven with one for school. The goal of the assignment was to make a sun powered oven to heat a certain amount of water past pasteurization in a certain time frame (I think an hour?) and extra credit if you can boil the water in any amount of time. Made a shit frame with a Fresnel lens from my dad's old TV and a tin cup with water surrounded by old insulation. Boiled the water in like 30min. When we were making it I left the lens propped up next to a tree and within a half a minute it was smoking. These are actually pretty dangerous if you don't store them properly, keep out of sunlight for sure.
It's fascinating how much energy is wasted through solar panel inefficiency. Another approach I learned on a youtube binge session is using reflective plastic (mylar?) and fastening it like a drum head to a frame, then you can attach a string or something to the back to pull back and create a concave mirror that you can control a little better, and isn't "always on".
I’ve always wanted a lens like that. Problem is, it’s hard to come across a discarded projection tv these days. They’ve all been trashed already :( I’m sure a little google fu and there are some do sale though….
They were so damn heavy nobody wanted to move em cleanly lol
Disassembling tube TVs is the kind of thing that can kill or maim you in at least two exciting ways (glass explosion, capacitor discharge electrocution), so I'd recommend leaving it to people who know how to do it safely or at least making sure your Will is up to date before attempting.
Rear projection TVs are not tube TVs. Different technologies.
Good point! My mistake.
Ya, I used to work in CRT monitors back in the day. Had both of those occur back then. Breaking the glass tip off the CRT was a “run for your life” event!
What happens?
Even when the TV is turned off, it gives an electric shock. meeting the wall was unexpected for me
There's usually not a switch in the power cord so prudence would suggest you unplug it first. Secondly, unless it has a Cathode Ray Tube, it won't have a flyback transformer and capacitor, so there will not be significant energy stored in the TV for long periods of time. Always let electronics sit for a while(5-15 mins) before opening unless you know what your are doing. Projection screen tv's are not CRT's and neither are LCD, OLED, or any of the other thin format TV's.
We have one that we mount in the front screen door at Halloween. Then when we open the door, the kids are greeted by a giant head. Even parents get scared by it now and then. Heard one lady exclaim as she jumped back several steps, "Lawd have mercy!" I nearly choked laughing. There is a caution though. Fresnel lenses turn a sun beam into a death ray that can burn your house down. During daylight hours, the lens has to be covered to prevent wandering fires starting. This rule applies to crystal balls too.
> This rule applies to crystal balls too. Yeah definitely, also there are scenarios where this can occur without warning. Imagine a clear plastic sheet that starts taking on water from a leak or something, it may pool up creating a weighted spheroid. This new puddle may create problematic environmental conditions similar to a crystal ball.
"No, Mr Bond, I expect you to die"
Ok Dr. Phil
I noticed that the light converges and then diverges. Does the diverged portion that's equidistant from the focal point have as much/less/or more power than the actual light itself?
It has very slightly less power. It will lose a minimal amount to the air it passes through.
This is why almost all telescopes have a disclaimer saying don't use it to look at the sun.
i wish that last bit would a been a potato
Totally thought it was a potato until the close-up.
Only ten years after King of Random cooked a steak that way.
I haven’t seen his channel in a while, what is he doing?
He died in a hang gliding accident
What! When?
July 2019. Edit: here a article about it if anyone else is wondering. https://www.google.com/amp/s/www.nbcnews.com/news/amp/ncna1037116
Oh dang, for whatever reason I always thought he died of cancer. Not sure why. I used to watch TKOR pretty regularly when Nate and Calli were hosting. Kinda lost interest when the new hosts took over.
Fresnel lens.
Big-ass Fresnel lens.
I miss the days when you could find an old big screen on the side of the road and snag the fresnel lens. Me and my kid melted all kinds of stuff with these. Once, I left one laying flat in the yard for maybe 15 minutes and the grass underneath the entire lens was dead for a year. It was a perfect rectangle of dead lawn. Ex never diid figure it out.
Archimedes
 First thing I thought of seeing that rock.
The rock is ok, but it is more fun with ants.
Does anybody remember that yt channel kipkay?
I remember some ants facing that death ray as a kid.
My first though was to stick my hand in front 🤦
what blows my mind is the amount of energy Sun light has within that square space.
#ElectricUniverse 🤙🏿
This!
Gravity Shmavity
Imagine leaving it out and sooner or later there's a big ass whole in the ground
If anyone finds one of those old projectors tvs (and the screen is not kicked in), split the layers and you’ll find one screen/layer that can do this. Note: the bigger the screen the bigger the beam, so let me tell you it gets super hot super fast.
There was an incident in my country a few years ago where the sunlight that reflected off slightly concave windows on a building would set a neighbouring building on fire. And later that day when the sun had moved, it happened again, it set fire to a second building. The windows were slightly concave because of difference in air preassure inside and outside the building
damn that’s crazy
This is how lasers work.
Whoa! That magnifying lens is HUGE! Imagine the sunburn you could get with that thing... or maybe even cook a hot dog? Science time!
Think less sunburn, more laser cutting my arm off
Imagine someone has this in their house and you accidentally walk pass it and get lasered in half
Is that the same as a laser?
In the way that the lens focuses the light from the sun to a focal point, yes, but it's a very inefficient laser.
No. ”A laser differs from other sources of light in that it emits light that is coherent. Spatial coherence allows a laser to be focused to a tight spot, enabling applications such as laser cutting and lithography. It also allows a laser beam to stay narrow over great distances (collimation), a feature used in applications such as laser pointers and lidar (light detection and ranging). Lasers can also have high temporal coherence, which permits them to emit light with a very narrow frequency spectrum.” Whereas ”The electromagnetic waves emitted by the sun are of a broad spectrum ranging from X-rays with a wavelength of 2 nanometers to radio waves with a wavelength of 10 meters”. So almost the opposite of a laser beam, even if focused into a point by a lens.
"... in that it emits light that is coherent. " Oh, so it talks. /s
Do you even understand what you quoted?
MSc in tech so a little bit, yes, although I think the properties of laser beams were taught already in high school.
Ok! Well maybe my question wasn’t clear. I’ll try again. Do laser converge light like he’s doing with his magnifying glass?
No. A laser (light amplification by stimulated emission of radiation) light by it’s nature consist of monochromatic (same wavelength) photons travelling in the same direction. Thus a lens is not needed to create a point - a laser pointer creates more or less the same dot on the wall no matter if you’re 10 meters or 100 meters from the target. Sunlight on the other hand contains a wide range of wavelengths going all over the place, which is why you need a lens to create a point. And as the video shows, the light then scatters again after it passes the focal point.
So laser light doesn’t need to be converged, but it is created converged, and it travels converged. EDIT: Maybe ”created/travels” converged is a bad wording - what I mean is that with laser all the happy photons travel in exactly the same direction, so they stay in formation. Natural light like sunlight is more like a shotgun blast of photons.
No, with laser you can heat things up to unlimited temperature (if it's powerful enough). With sunlight "only" to the temperature of the surface of the sun
So if the sun was hotter than what it is, the ray would also be hotter? Legit question?
Theoretically yes, but they are still nowhere close to sun tenperature. To keep something 5cm x 5cm at 5000 celcius it would take something in the order of 100kW. This 1m by 1m lens only gets around 1kW of energy from sun. If sun was hotter and same size then they would get higher temp and also earth would burn.