Question

In thin-film interference, an interference pattern is formed...

A. due to the imperfections (such as dust or debris) contained within the thin film that absorbs some of the spectrum of the light in the film.

B. due to the light reflecting off the bottom layer of the film traveling a different number of wavelengths compared to the light reflecting off the top of the film

Answer 1

The right answer is Option B.

In thin film interference, if the thickness of the film is an odd multiple of a quarter of the wavelength of the light reflected on it, there is destructive interference that results in destructive interference of that particular wavelength. The opposite takes place when the thickness is a multiple of half the wavelength of the light, the opposite happens. As such, when white light consisting of many wavelengths is incident on a thin film, some wavelengths get attenuated while some get intensified.