Colours reflected from an oil film on water depend on all of the following factors EXCEPT

Explanation

The thickness of the film is a critical factor in thin-film interference, which governs the colors reflected from an oil film on water. The interference pattern depends on the path difference between light waves reflected from the top and bottom surfaces of the film. The density of the oil does not directly affect the color reflection, as it is more relevant to the physical properties rather than optical properties. The angle of view affects the path difference and thus the interference pattern, making it influential in the observed colors. The index of refraction influences how light waves bend and interfere within the film, affecting the reflected colors. Therefore, the correct answer is the thickness of the film, as it is least related to the direct observation of colors from the film.