Due to interference, a thin film reflects no orange light...it appears dark. If you double its thickness and illuminate it again with orange light, what will you see? Choose one answer only.
It will appear dark again.
It will appear bright (strongly reflecting the orange light).
It could be either bright or dark, depending on the film.
no knowing whether a phase shift has occurred at both or just one boundary, it could be bright or dark.
This answer was incorrect
If a thin film reflects no orange light and appears dark, it means there is destructive interference happening between the incoming and reflected waves of the orange light. Destructive interference occurs when the peaks of one wave align with the troughs of another, leading to cancellation and resulting in low or no intensity of light being reflected.
If the thickness of the film is doubled, the path length difference between the original and reflected waves will also double. This change in thickness affects the phase relationship between the waves, potentially leading to different interference patterns and outcomes.
In general, if the change in thickness results in a path length difference that is exactly half of the wavelength of the orange light (λ/2), the interference can switch from destructive to constructive. Constructive interference occurs when the peaks of one wave align with the peaks of another, resulting in enhanced amplitude and brightness.
Therefore, in this scenario, if the doubled thickness generates a path length difference of λ/2, the previously dark film can switch to appearing bright and strongly reflecting the orange light. However, if the path length difference is still a multiple of the wavelength (λ), destructive interference will continue to occur, and the film will appear dark again.
So, the correct answer is: It could be either bright or dark, depending on the film.