Video Transcript
Fill in the blanks. The postulated thickness of the
ozone layer under normal pressure at zero degrees Celsius is blank. This thickness corresponds to blank
Dobson units. (A) 20 kilometers comma 200. (B) Three millimeters comma
300. (C) 300 millimeters comma
three. (D) 15 millimeters comma 150. (E) 15 kilometers comma 200.
The ozone layer is part of the
Earth’s atmosphere, and it is located within the stratosphere. The stratosphere is the second
layer of the Earth’s atmosphere, and it is located at a height of between 10
kilometers and 50 kilometers from the Earth’s surface. Most of the ozone formed within the
stratosphere is found at a height of between 20 kilometers and 40 kilometers from
the Earth’s surface.
Ozone gas is a molecule composed of
three oxygen atoms bonded together. The precise concentration of ozone
in the stratosphere varies with the altitude. One way of measuring the
concentration of ozone in the atmosphere is to imagine a column of atmosphere rising
from the Earth’s surface to the edge of space. We could then see how thick the
layer of pure ozone molecules would be if they were concentrated at the surface of
the Earth and measured under normal atmospheric pressure. For this measurement, the
temperature would also need to be zero degrees Celsius. We would find that the average
thickness of a pure ozone layer contained under these conditions is just three
millimeters.
If the layer produced from all the
atmospheric ozone was just one millimeter thick, then we would define the
atmospheric concentration of the ozone as 100 Dobson units. Since the layer produced by normal
atmospheric concentrations of ozone under these conditions is three millimeters
thick, this equates to 300 Dobson units. So the postulated thickness of the
ozone layer under normal pressure at zero degrees Celsius is three millimeters. This thickness corresponds to 300
Dobson units. Three millimeter comma 300 is the
correct answer.
