Image: Electric glow discharge schematic

Description: An electric glow discharge tube (Crookes tube) showing the different glowing regions in the gas that appear when a high DC voltage is applied between the electrodes:
Title: Electric glow discharge schematic
Credit: http://en.wikipedia.org/wiki/File:Electric_glow_discharge_schematic.png
Author: http://en.wikipedia.org/wiki/User:Iantresman
Permission: .mw-parser-output .responsive-license-cc{clear:both;text-align:center;box-sizing:border-box;width:100%;justify-content:space-around;align-items:center;margin:0.5em auto;background-color:#f9f9f9;border:2px solid #e0e0e0;border-spacing:8px;display:flex}.mw-parser-output .responsive-license-cc div{margin:4px}.mw-parser-output .rlicense-text div{margin:0.5em auto}@media screen and (max-width:640px){.mw-parser-output .responsive-license-cc{flex-flow:column}.mw-parser-output .rlicense-text{order:1}} This file is licensed under the Creative Commons Attribution 2.5 Generic license. You are free: to share – to copy, distribute and transmit the work to remix – to adapt the work Under the following conditions: attribution – You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.https://creativecommons.org/licenses/by/2.5CC BY 2.5 Creative Commons Attribution 2.5 truetrue Created by Ian Tresman (22 Mar 2006)
Usage Terms: Creative Commons Attribution 2.5
License: CC BY 2.5
License Link: https://creativecommons.org/licenses/by/2.5
Attribution Required?: Yes