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Where is ozone most abundant in the atmosphere?
  • A
    Close to the surface in the troposphere.
  • B
    Close to the tropopause.
  • C
    Within the stratosphere and with a relatively high concentration at around 30 km above the surface of the Earth.
  • D
    Approximately at 18 000 ft in the troposphere.

Refer to figure.
Ozone is a gas that is naturally present in our atmosphere. Each ozone molecule contains three atoms of oxygen and is denoted chemically as O3. Ozone is found primarily in two regions of the atmosphere. About 10% of atmospheric ozone is in the troposphere, the region closest to Earth (from the surface up to about 10–16 kilometres). The remaining ozone (about 90%) resides in the stratosphere between the top of the troposphere and about 50 kilometres altitude. The large amount of ozone in the stratosphere is often referred to as the “ozone layer.”

The ozone layer is a thin part of the Earth's atmosphere that absorbs almost all of the sun's harmful ultraviolet light. Unfortunately, it is also toxic to humans. This means that the ozone concentration at jet cruising levels can be enough to be hazardous to humans, as is detailed in Learning Objective 050.01.01.03.02.

The ozone layer is found in the stratosphere. Refer to the annex above for a visual representation of a normal ozone distribution.

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