Chapter 14, Problem 12RQ

To determine

The reason behind variety of colors is seen in gasoline splotches on wet street.

Explanation of Solution

A variety of colors is seen in gasoline splotches on wet streets that occur due to the interference of light reflected from inside as well as outside the surfaces. When a color is canceled, its complementary colors are observed. This occurs in gasoline on a wet street also. Light reflects from two surfaces. One is the upper, air-gasoline surface. The other is the lower gasoline-water surface.

Since the film thickness is not uniform, different film thickness shows a contour map of microscopic differences in surface elevation.

Conclusion:

Therefore, a variety of colors are seen in gasoline splotches on wet street is due to the non uniform thickness of the film which results in showing a contour map of microscopic differences in surface elevations.