 The effect is a form of electroluminescence where incoherent and narrow-spectrum light is emitted from the p-n junction in a solid state material.The first practical visible-spectrum LED was invented in 1962 by Nick Holonyak Jr.

1962 Electret microphone

An electret microphone is a type of condenser microphone, which eliminates the need for a power supply by using a permanently charged material.Electret materials have been known since the 1920s, and were proposed as condenser microphone elements several times, but were considered impractical until the foil electret type was invented at Bell Laboratories in 1962 by Jim West, using a thin metallized Teflon foil.