Reflection of light off film, wavelength and thickness?

[mithraz87]

What is the thinnest film of MgF2 (n = 1.39) on glass that produces a strong reflection for light with a wavelength of 680 nm?

This is the exact question I am faced with. I didn't really know where to begin so I tried using the ratio of n-air/wavelength to n-film/(new wavelength) to try and find the original wavelength. I found that, and really didn't know where to go then. I have looked around, and I just can't seem to find anything. Any help would be greatly appreciated.

 

[alphysicist]

Hi mithraz87,

What is the thinnest film of MgF2 (n = 1.39) on glass that produces a strong reflection for light with a wavelength of 680 nm?

This is the exact question I am faced with. I didn't really know where to begin so I tried using the ratio of n-air/wavelength to n-film/(new wavelength) to try and find the original wavelength. I found that, and really didn't know where to go then. I have looked around, and I just can't seem to find anything. Any help would be greatly appreciated.

From your post, I was wondering if you asking what type of problem this is? This problem is dealing with the interference by thin film; I would think that your textbook has at least a section devoted to the topic with some examples.

You can also look at http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/thinfilm.html#c1

Does that help? If you are still stuck, post what you have tried.