video
https://en.wikipedia.org/wiki/Led
https://en.wikipedia.org/wiki/Led_Zeppelin
https://en.wikipedia.org/wiki/LED_lamp
https://en.wikipedia.org/wiki/Led_Zeppelin_II
Mini Led Flashlight with LT1073 IC – ElectroSchematics.com
High power LED flashlight circuit with 1.5V AA battery
How Does A Flashlight Work | Energizer