Passage VI

Air at its dew point temperature (or dew point) is saturated with water vapor. Air temperature usually decreases with increasing altitude. When air cools to its dew point, the water vapor in the air can begin to condense and form clouds.

Air temperatures and dew points were measured every 600 m from the surface (0 m) to an altitude of 3,000 m at 4 cities (A-D). Data, including the altitude of the cloud base over each city, were taken at 2 P. M. on every summer day that clouds were present. Figures 1-4 show the average air temperatures, the average dew points, and the average cloud-base altitudes at each city.

32. A ceilometer bounces a light beam off the base of a cloud layer and measures how long it takes the light to make the trip up and back. The scientists who made the measurements plotted in Figures 1-4 most likely used the ceilometer to determine which of the following data?

Answer and Explanation

Your Answer is

Correct Answer is H

Explanation

The ceilometer mentioned in the question stem mainly calculates the height of the cloud layer by measuring the round-trip time between the instrument and the cloud layer. Altitude=t×C/2, C is the speed of light, and time is the round-trip time of light