We see barcodes everyday and almost every where.
Before the invention of barcodes, cashiers at stores have to run their deft little fingers across the cash machines to register payment.
Now, they just have to beep all items under their scanners. What convenience that little piece of black and white stripes sticker provides!!
Recall what you've learnt under the topic Light - how does an object appear white / red / black?
When white light shines on an object and it reflects the whole spectrum into our eyes, we'll see white. On the other hand, if the object absorbs all light and reflect none, we'll see it as black.
Barcode makes use of the different reflective behaviour of black and white surfaces to transmit data. A scanner (usually we just see a thin ray of red line flashing on the barcode) will record the pattern of reflection from the barcode and send it to a reader in the cashier.
Imagine the snaking queue we have to endure without those clever little barcode stickers!
