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How I got my laser eye injury

funraniumlabs.com

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Re: How I got my laser eye injury

#261

Post by donw »

edscho wrote: post #258
porknubbins wrote: post #250

Earlier quoted context omitted.

Brits don’t mess around with tea I guess. I believe they’re mostly on 240v even for residential there. Correct me if I’m wrong but I don’t think it would even be possible to heat water that fast in the US on 120v.

Correct, it takes about twice as long to boil a kettle in the US. But the US is the anomaly here. Most countries use 220-240V mains like Britain [1]. [1] https://en.wikipedia.org/wiki/Mains_electricity_by_country#T...

Technically, the US does as well.

You have 240 V at the panel, but you only run half for each common circuit.

Re: How I got my laser eye injury

#262

Post by wbl »

porknubbins wrote: post #250
sebastiennight wrote: post #249

Earlier quoted context omitted.

This seemed like a wild claim (2500 watts for a tea kettle!? As much as a microwave oven in full blast?) so I looked it up. Wow.

Brits don’t mess around with tea I guess. I believe they’re mostly on 240v even for residential there. Correct me if I’m wrong but I don’t think it would even be possible to heat water that fast in the US on 120v.

They have a man watch the telly to hit the button to turn on the power for all the teapots going on. https://www.youtube.com/watch?v=slDAvewWfrA

Re: How I got my laser eye injury

#263

Post by MengerSponge »

edscho wrote: post #258
porknubbins wrote: post #250

Earlier quoted context omitted.

Brits don’t mess around with tea I guess. I believe they’re mostly on 240v even for residential there. Correct me if I’m wrong but I don’t think it would even be possible to heat water that fast in the US on 120v.

Correct, it takes about twice as long to boil a kettle in the US. But the US is the anomaly here. Most countries use 220-240V mains like Britain [1]. [1] https://en.wikipedia.org/wiki/Mains_electricity_by_country#T...

British outlets are individually fused so they're typically rated for more current

Re: How I got my laser eye injury

#265

Post by wruza »

jnwatson wrote: post #73

Rule number 1 of laser safety is "do not look into beam with remaining eye".

When I was a kid, I tried to look at it and nothing happened just like my friends said. All warnings failed to deliver a message that eye damage may be delayed and invisible at first. I didn’t lose sight after 30 years, so that laser was probably safe, but for fucks sake can they write non-dismissable warnings instead?

Reminds me that stupid low bridge warning: “overheight must turn”. Instead of messaging to a driver that they are overheight right now it just reads as a general rule. Numerous incidents per year as a result.

Re: How I got my laser eye injury

#266

Post by gibspaulding »

zoky wrote: post #3

I’m not saying it didn’t happen as described, but this really kinda reads like the “Bald eagle named Albert Einstein flew into the classroom” copypasta…

It reads like most Funranium Labs posts. Here are some other good ones:

https://www.funraniumlabs.com/2015/04/an-april-fools-caution...

https://www.funraniumlabs.com/2018/09/the-fringes-of-regulat...

Re: How I got my laser eye injury

#267

Post by schoen »

One of the important safety lessons that non-experts could take from this story is that protective eyewear for lasers can be highly specific to the kind of laser (as lasers have only a single wavelength, the eyewear may be designed to filter out that specific wavelength rather than attenuate light-in-general). I once knew this but had forgotten it, and some of the people in the story apparently never knew it.

Also the mirror and low-divergence thing are so scary. Much like laser microphones! We have a pretty deep human intuition that other people must be at least somewhat close by in order to harm us, and lasers break that intuition.

Re: How I got my laser eye injury

#268

Post by amluto »

oh_my_goodness wrote: post #224
tlb wrote: post #100

Earlier quoted context omitted.

Why don't welding/cutting lasers add more divergence with built-in optics? Would it hurt performance? It seems like you could add 1 mrad and it would hardly make a difference at the usual working distance, but spread out to a meter over 1 km, so you can't zap people across town.

If it's a 1-micron wavelength laser with a 60 micron radius spot, the divergence can't be much less than about 5.7 mrad half angle. What makes eye safety tricky is just that 2.5 million milliwatts is a lot of power. Even when you spread it out some.

On the other hand, 2.5kW of light is not outrageous. It’s not drastically higher than some of the larger theatrical lights. (Not that being in a spotlight is pleasant, but it does not permanently blind the actors.)

A lot of this comes down to wavelength. Some wavelengths get focused by one’s eye and can concentrate their power in a small spot on the retina. Other wavelengths will be absorbed before they get to the retina and will therefore deposit their power over a larger area and in less sensitive tissue.

It can also make a difference if the light is pulsed.

Re: How I got my laser eye injury

#269

Post by cwillu »

MengerSponge wrote: post #263
edscho wrote: post #258

Earlier quoted context omitted.

Correct, it takes about twice as long to boil a kettle in the US. But the US is the anomaly here. Most countries use 220-240V mains like Britain [1]. [1] https://en.wikipedia.org/wiki/Mains_electricity_by_country#T...

British outlets are individually fused so they're typically rated for more current

British outlets are fused for _lower_ current than american outlets, not more: 13 amps instead of the 15 or 20 that's common here. It's the voltage that's higher, which means that the power transferred for a given current is about double.

Re: How I got my laser eye injury

#270

Post by SXX »

talldayo wrote: post #238
SXX wrote: post #231

Earlier quoted context omitted.

Is it scientifically proven though? If it that powerful wouldn't it cook your brain as well?

If the radar is located on the ground, the chances are it's consuming enough energy to cook a turkey from the inside-out.

Yeah, but one that immediately make you sterile will likely burn out your eyes and cook the brain. In any case I was just pointing out this is urban legend of sorts.
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