Thin-film interference is observed when polychromatic light is incident on an interface formed by two semitransparent media. Which of the following best explains why thin-film interference generates a multicolored array when two semitransparent fluids are used?

Question

Thin-film interference is observed when polychromatic light is incident on an interface formed by two semitransparent media.  Which of the following best explains why thin-film interference generates a multicolored array when two semitransparent fluids are used?

Quizplus · Accepted Answer

11ecba2d_1318_7fea_a3bf_6f863feddfb5_MD0008_00 Thin-film interference refers to the multicolored arrays generated by the reflection events that occur within a system composed of two layers of semitransparent media. The relative intensity of the colors seen within the multicolored array depends on the constructive and destructive interference among waveforms of polychromatic (variable wavelength) light. Interference that occurs within a thin-film system results from differences in the travel path of the light. Some light that is incident on the two-media system will reflect off the surface of the first medium (thin film), and some light will transmit through the first medium before reflecting off the media interface. When light reflected off the surface of the first medium constructively interferes with light reflected off the media interface, an observer perceives bright light. Conversely, when light reflects off the surface of the first medium and destructively interferes with light reflected off the media interface, an observer perceives darkness. Thin-film interference is influenced by the thickness of the film because light waves of a specific wavelength (ie, color) that interfere constructively or destructively at one film thickness may no longer interfere in the same fashion at a different thickness. Therefore, surface tension and other effects that locally distort the surface of a fluid may also cause multicolored arrays to appear on the surface as light that emerges from adjacent segments of the thin film varies in color composition. (Choices A and C) Variations in fluid density and osmolarity cannot explain changes to the interference pattern of light that are necessary to produce multicolored arrays. Furthermore, the fluid density and osmolarity of each medium would not be expected to vary within the same two-media system. (Choice D) Layering two semitransparent fluids increases the frequency of reflection events, enabling the waveform interference that generates multicolored arrays. Educational objective: Thin-film interference describes the multicolored array generated when polychromatic light is incident on an interface formed by two semitransparent media. Localized discrepancies within the thickness of a thin film (top media) contribute to variable interference patterns that produce the colorful array.

Thin-Film Interference Is Observed When Polychromatic Light Is Incident on an Interface