CBSE Class 12-science Answered

The presence of dangerous gases in mines may be detected by means of beats .The apparatus consists of two identical pipes; one blown from the air from reservoir and other by the air in the mine. If the two airs are the same,the two pipes will give the notes of same frequency.But if the air in the mines is polluted with dangerous gases, these lighter gases would be having a greater velocity of sound waves and that pipe will give a note of higher frequency. this will produce beats. Thus, the method serve as an early warning system to safeguard workers against possible dangerous explosions.