Explanation: Air Pressure can be defined as the pressure of air in the earth's atmosphere. It reaches a maximum of about 100,000 Pa near sea level and decreases as altitude increases.

The barometer is an instrument which is used for measuring Air pressure.

Physics instruments and their uses:

Barkometer - - - Tanning liquors used in tanning leather
Bolometer - - - Electromagnetic radiation
Spectrometer - - - Properties of light.