ABSTRACT
Light emitting diodes, usually known as LEDs, give off light when a current flows through them. The original LEDs were red, but now there are orange, yellow, green, blue and white LEDs. There are also infrared LEDs, which produce infrared instead of visible light. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780080959153/a02e7bef-ec09-4853-831d-9795f01199b3/content/fig21_1_OB.jpg" xmlns:xlink="https://www.w3.org/1999/xlink"/> https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780080959153/a02e7bef-ec09-4853-831d-9795f01199b3/content/fig21_2_OB.jpg" xmlns:xlink="https://www.w3.org/1999/xlink"/>
