Chapter 31, Problem 31A

Figure 31.19 shows destructive interference of blue light waves reflected from the top gasoline surface and from the top water surface. If white light is incident at the same angle, the eye sees yellow light. Would changing the viewing angle still produce yellow light? Would changing the thickness of the gasoline layer still show yellow? Defend your answers.

To determine

To explain: Whether changing the viewing angle would still produce yellow light or not.

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. And if the crest of the one wave falls on the trough of the other wave then it is said to be destructive interference.

If we change the viewing angle, the same yellow color will not be seen by the eye. But, due to change in the path length of the light wave, another color can be seen. Similarly, by changing the thickness of the gasoline layer, there will be no yellow light produced. Because changing the thickness as well as the viewing angle will affect the path length and eye will see different color instead of yellow.

Conclusion:

No, by changing the thickness or viewing angle yellow light cannot be seen.