Chapter 31, Problem 32A

(a)

To determine

The color that the eye sees.

Answer to Problem 32A

Blue color.

Explanation of Solution

Introduction:

A thin film like a soap bubble has two surfaces that are closely spaced. Light reflecting from one surface can cancel out the light reflecting from the other surface.

When the thin film is illuminated with the white light, then after cancelling out one color the other complementary color appears. So, when yellow light is cancelled, the complementary color that appears will be blue.

Conclusion:

So, the color that the eye sees is the blue color.

(b)

To determine

The reason why the color will change when the surface is viewed at a grazing angle.

Explanation of Solution

Introduction:

A thin film like a soap bubble has two surfaces that are closely spaced. Light reflecting from one surface can cancel out the light reflecting from the other surface.

When the viewing angle is changed, then the other color will appear because the path length will be changed due to the changed viewing angle. Hence, the longer path length will cancel the wavelength of the light which is longer.

Conclusion:

Hence, the color will change when the viewing angle is changed.