When we breathe in, the inhaled air can contain dust, chemicals and other irritants that can be harmful to the body, particularly to organs in the respiratory system like the lungs. While the tiny hairs inside the nostrils (cilia) trap many of these particles, some will often get through. To help you out, your body reacts to try and forcibly expel the offending particles via the sneeze reflex arc.
There are a number of other reasons why we sneeze, including to clear the nasal passages when you have a cold, to expel allergens if you are allergic to something, and even bright sunlight can cause some people to sneeze.
When a stimuli is detected by the nerve endings in the nose, impulses are sent to the brain, which initiates a chain of physiological events that enable the body to rid itself of the unwelcome item.
Barcodes are a machine-readable way of writing letters and numbers. A laser is shone onto the barcode and the reflected light can be interpreted by the barcode reader. There are many types of barcodes, but the ones most commonly found in supermarkets use a row of lines of different widths.
The different widths represent different numbers. In the UK many items are coded with a GTIN – Global Trade Item Number. This allows the manufacturer to print the barcode on the packages. The numbers are unique to that item. The barcode only has a number, but no product information.
That is held in a database which the retailer can access at the point of sale. It also means that shops can set their own prices and change them easily.