Anti-Reflecting coatings on a glass lens

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To eliminate back reflection from a glass lens with an anti-reflection coating, the minimum coating thickness can be calculated using the principles of destructive interference. For a helium-neon laser at 632.8 nm, the thickness of the magnesium fluoride film should be one-quarter of the wavelength in the coating material, which is approximately 114 nm. The coating should ideally be applied to both the front and rear faces of the lens to achieve optimal performance and minimize reflections. Understanding thin film interference is crucial for determining the correct thickness and ensuring effective anti-reflection properties. Proper application of these principles will enhance the lens's optical performance.
BananaMan
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heres the question:

anti-reflection coatings on a glass lens (n=1.50) consists of a magnesium fluoride (n=1.38) film, the coating thickness is chosen to eliminate any back reflectionusing the ideas of destructive interference. What is the minimum coating thickness required to eliminate the reflection from a helium-neon laser at 632.8nm? Should the coating be the same thickness on both the front and rear faces of the lens?

really don't have a clue where to go with this one, looked all through my notes for this and can't find anything on coatings, if someone could just point me in the right direction i should be able to do it? thanks
 
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