What does a barcode reader emit to identify bar codes?

A barcode reader emits a beam of light, typically from a laser or LED, to scan the barcode. When the light hits the barcode, it reflects back differently depending on the pattern of black and white bars. The reader captures the reflected light and converts it into an electrical signal, which is then processed to identify the encoded information. This allows the reader to translate the barcode into a readable format, such as a product number or description.