Wavelength nature of light: magnesium Fluoride

[Dx]

Hi!

In terms of magnesium fluoride what is the minimum thickness of mag fl coating that must be applied to a glass lens to make it non-reflecting for that wavelength? (the index of refraction of magnesium fluoride is intermediate to that of air and glass)

1/2 wavelength out of phase to eliminate reflection. why is this wrong? I usd the formula t = [lamb] / 4n. I used the minimum thickness (m=0) since the destructive interference will occur over the widest angle. Plz help? Or it this a trick question and there is no minimum thickness, huh?
Dx

 

[quantumdude]

Originally posted by Dx
I used the minimum thickness (m=0) since the destructive interference will occur over the widest angle.

Obviously, they mean the minimum nonzero[/color] thickness. "Zero thickness" means that there is no film at all.

 

[Dx]

Originally posted by Tom
Obviously, they mean the minimum nonzero[/color] thickness. "Zero thickness" means that there is no film at all.

Its not that obvious Tom since that's not one of the answers. I understand what your saying so I need to figure out the different wavelengths then, huh?
Dx

 

[drnikitin]

Originally posted by Dx
why is this wrong? I usd the formula t = [lamb] / 4n. I used the minimum thickness (m=0)
Dx [/B]

You are right. The minimum thickness of the coating is given by t=[lamb]/4n. I think you did an error in calculations. Check it please.

 

[quantumdude]

Originally posted by Dx
I usd the formula t = [lamb] / 4n. I used the minimum thickness (m=0) since the destructive interference will occur over the widest angle.

OK, sorry. I didn't know what m was, and I thought you chose the thickness to be zero.