It was almost impossible to make the blue LED [video] • Hacker News Board

Re: It was almost impossible to make the blue LED [video]

#201

Post by jaybrendansmith » Sun, Feb 11, 2024, 2:30 PM UTC

AlexCoventry wrote: post #161

metadat wrote: post #156

Amazing and inspiring story about perseverance and never giving up. https://images.squarespace-cdn.com/content/v1/595d3fb837c581... Though it is incredibly frustrating how ungrateful Nichia Corp was to Mr. Nakamura, the underdog who pushed through every obstacle to ultimately give them the vehicle for more than 65% of their revenue! People like the Nichia CEO at the time, a nephew who inherited the business nepotism-…

I think it was narcissism. Nakamura ignored direct orders to desist for years, and wound up proving that those orders were massive strategic blunders. So insubordination combined with making his superior look a fool. (On the other hand it's pretty clear we're only getting Nakamura's side of the story.)

It's not narcissism. I have dealt with this situation myself. It's recognizing that the boss is in over his head technically and is making the wrong decisions. This situation happens when the researcher cannot explain clearly why he knows a particular strategy is the correct one or why he knows it will work. Yes, it's confidence of a particular kind, one that you get when you understand every detail, and it requires trust.

Re: It was almost impossible to make the blue LED [video]

#202

Post by chopin » Sun, Feb 11, 2024, 7:45 PM UTC

pavel_lishin wrote: post #194

fernmyth wrote: post #191

Earlier quoted context omitted.

The lenses in your eyes refract different wavelengths at different angles - think of a rainbow coming out of a prism. Only one wavelength can be perfectly tuned to project a clear image onto your retinas. We are optimized for green, red is close enough, but blue always looks blurry.

Huh, I like that theory. Nobody else has ever mentioned experiencing the same thing as I do, though.

It's called color aberration and a big thing in telescopes using lenses.

Re: It was almost impossible to make the blue LED [video]

#203

Post by jldugger » Mon, Feb 12, 2024, 2:35 AM UTC

amelius wrote: post #27

I'm looking for __pink__ leds, but can't find a good source. Digikey has only very limited options with many packages like 0805 missing.

"This LED needs to be light red. NOT PINK! LIGHT! RED!"

Re: It was almost impossible to make the blue LED [video]

#204

Post by itishappy » Mon, Feb 12, 2024, 4:05 PM UTC

amarant wrote: post #142

01HNNWZ0MV43FF wrote: post #133

Earlier quoted context omitted.

I liked it, though it bugs me a little when people equate infrared and heat. Infrared is light. Light can heat things, and hot things can glow, but "infrared is heat" isn't exactly right.

I know basically nothing about physics, so sorry if this is a dumb question. The existence of infrared LEDs seems to indicate to me that infrared light can exist without heat. The existence of infrared thermometers seems to imply that hot stuff radiates infrared light, at least usually. So my question is, is there any case where heat does not cause infrared radiation? What are those cases? Some special materials? Spe…

The concept you're looking for is called Emissivity, and it describes how effectively an object can radiate (or absorb!) at a certain wavelength.

https://en.wikipedia.org/wiki/Emissivity

> Real objects never behave as full-ideal black bodies, and instead the emitted radiation at a given frequency is a fraction of what the ideal emission would be. The emissivity of a material specifies how well a real body radiates energy as compared with a black body. This emissivity depends on factors such as temperature, emission angle, and wavelength. However, it is typical in engineering to assume that a surface's spectral emissivity and absorptivity do not depend on wavelength so that the emissivity is a constant. This is known as the gray body assumption.

https://en.wikipedia.org/wiki/Black-body_radiation

In a previous life I worked for a lab designing a passive radiator that was reflective to visible light but absorptive/emissive in the atmospheric window (where the atmosphere is completely transparent). This material had the fun effect of absorbing energy via conduction/convection and then sending it out into space, maintaining a temperature slightly below ambient.