So how many stars are there in the Universe? It is easy to ask this question, but difficult for scientists to give a fair answer! Stars are not scattered randomly through space, they are gathered together into vast groups known as galaxies. The Sun belongs to a galaxy called the Milky Way.
Reverse osmosis. Reverse osmosis (RO) is a water purification technology that uses a semipermeable membrane to remove ions, molecules, and larger particles from drinking water.
LIMITATION OF FILTERS Chemical Filters Chemical filters are used on respirators to help remove and lower worker exposures to harmful gases and vapours in the workplace. There are several types of chemical filters: ï· Organic vapour. ï· Inorganic vapour.