Chapter 31, Problem 30A

If you notice the interference patterns of a thin film of oil or gasoline on water, you'll note that the colors form complete rings. How are these rings similar to the lines of equal elevation on a contour map?

To determine

To explain: The similarity of the rings to the lines of equal elevation on a contour map.

Explanation of Solution

Introduction:

The superposition of the two light waves can be defined as the interference of light. When the crest of the one wave overlaps with the crest of the second wave then the interference is said to be constructive, if the crest of the one wave falls on the trough of the other wave then it is said to be destructive interference.

Interference in the thin films of the light waves of mixed frequencies produce colors which can be seen in these thin films. And the phenomenon is known as iridescence. Due to the interference pattern of a thin film of oil or gasoline, the colors which form the complete rings are relatable to the lines of elevation. Just like this elevation, each color due to the interference pattern represents an elevation above the surface of water.

Conclusion:

Hence, the complete rings are similar to the lines of elevation on a contour map.