LEDs And Lasers Dunked In Liquid Nitrogen

you can do this easily with frequency summation lasers, putting a yellow frequency summation in a freezer will make it shift to green... warming it will shift it to red, it's very cool
 
You could use this as an accurate temperature measurement. Given that we have lots of those.
 
So why do all of the light sources in the sky show up as white to the human eye, but our sun shows up as yellow? Just closer? Or I'm a blind bat? (Taking the concept to a different scale).

Or is this just a LED electronics thing?
 
My work has a dedicated LN2 safety manager and he would probably freak at the complete lack of safety gear.
 
Needs more accidental blinding while staring at reflected laser light and aiming lasers that are dangling by power leads at each other's bodies.
 
cageymaru said:
So why do all of the light sources in the sky show up as white to the human eye, but our sun shows up as yellow? Just closer? Or I'm a blind bat? (Taking the concept to a different scale).

Or is this just a LED electronics thing?
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If you are far enough away from light pollution and let your eyes adjust, you will see that some of those "white" stars are different colors. Some are more blue and others closer to red along with those that are shades somewhere in between the two.
 
cageymaru said:
So why do all of the light sources in the sky show up as white to the human eye, but our sun shows up as yellow? Just closer? Or I'm a blind bat? (Taking the concept to a different scale).

Or is this just a LED electronics thing?
Click to expand...

I assume you mean stars as "all those light sources" ?? :)

Sun looks yellow when it's high over head due to Rayleigh scattering, basically molecules of air scatter bluer wavelengths much more easier, also why the sky is uniformly blue. When the Sun is near the horizon it's closer to red than yellow, because more atmosphere for the light to go through before it reaches you, so even longer wavelengths (yellows) end up getting scattered.

Now why do other stars look white? Well part of it is you being a blind bat ;) The brightest stars might have a blue or red appearance to them, the rest tend to look white. The reason for this is biology, because in your eye you have two types of photoreceptors, cones which you're mostly using right now to read this, they're very sensitive to colors and what not, and rods, which are very sensitive to light in general but not very sensitive to color. At night the cones in your eyes tend to "power off" while the rods tend to "power up" this is what we typically refer to as "night vision", the rods being more sensitive to light can pick up fainter light sources (it's why it hurts when you leave a movie theater during the day too, lots of rods in the dark theater, and you walk out into the bright sun they get over stimulated = pain), however our cones are not as sensitive to faint light sources and those pick up all the color that we see, now for the brightest of stars there's just enough light there for our cones to pick up so we can see a faint blue or red tinge to various stars (Orion = blue, Betelgeuse = Red), most of the stars are not as bright though, so they will look more white (just what our brain says "hey there's a light source, this is what it looks like").

Even though stars and semi-conductors make light in different ways, stars do give off different wavelengths (strength of wavelengths) based upon the temperature they are. In the opposite way of this video though, cooler = shorter wavelengths in the LED/Laser, in stars hotter = shorter wavelengths.
 
viscountalpha said:
yeah. those kids were doing some very dumb stuff safety wise.
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Not sure about that, it's reasonably safe. Just don't stick you hand in there! :p Safer than a lot of crap I did as a kid anyway. Kind of makes me shudder looking back. :eek:
 
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