Answer
See explanation.
Work Step by Step
This is explained using the principles on page 1172. In the case of the soap bubble, reflected light undergoes a phase change of $\pi$ rad at the air-water interface, and no phase change at the subsequent water-air interface. The 2 reflected beams destructively interfere, and the thin bubble looks black.
When the soap is on glass, with a higher index of refraction than water, reflected light undergoes a phase change of $\pi$ rad at the air-water interface, and a phase change of $\pi$ rad at the subsequent water-glass interface. The 2 reflected beams constructively interfere, and the film looks shiny.
