Anti-reflective coating confusion

In summary, the thickness of an anti reflection coating should be expected to increase for incidence slightly away from normal, according to the equation 2ndcos(Θ) = mλ. However, this may seem contradictory to the intuition that the thickness should decrease due to the longer distance the waves have to travel through the material. This is because the extra distance the first reflected wave must travel must also be taken into account.
  • #1
Solarmew
37
1
My professor confused me today :(
I'm trying to figure out the thickness of an anti reflection coating and it looks like from the equation
2ndcos(Θ) = mλ
that for a given λ the thickness of the film should increase for incidence slightly away from normal.
But he said that intuitively it should decrease because the waves now have to travel a longer distance through the material... which kinda makes sense, but contradicts the equation.
Could someone please explain to me exactly what it happening and whether the thickness should be expected to increase or decrease if we increase the angle and why?
@.@
 
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  • #2
Solarmew said:
My professor confused me today :(
I'm trying to figure out the thickness of an anti reflection coating and it looks like from the equation
2ndcos(Θ) = mλ
that for a given λ the thickness of the film should increase for incidence slightly away from normal.
But he said that intuitively it should decrease because the waves now have to travel a longer distance through the material... which kinda makes sense, but contradicts the equation.
Could someone please explain to me exactly what it happening and whether the thickness should be expected to increase or decrease if we increase the angle and why?
@.@
The distance that the 2nd reflected wave travels through the film will increase, but that's not the full story. You also need to consider the extra distance the first reflected wave must travel (due to things being at an angle).

Follow the derivation, given here: Interference Condition for Thin Films
 

What is anti-reflective coating and what does it do?

Anti-reflective coating is a thin layer of material that is applied to the surface of lenses or other optical devices to reduce the amount of glare and reflections. This improves the clarity and sharpness of vision, making it easier to see through the lens.

How does anti-reflective coating work?

Anti-reflective coating works by reducing the amount of light that is reflected off the surface of the lens, allowing more light to pass through and reach the eye. It does this by creating a barrier that interferes with the reflection of light waves, ultimately reducing glare and improving vision.

What are the benefits of using anti-reflective coating?

Some of the main benefits of using anti-reflective coating include improved vision, reduced eye strain, and increased visual comfort. This can be especially beneficial for those who wear glasses or work in environments with bright lights or screens.

Is anti-reflective coating necessary for all lenses?

No, anti-reflective coating is not necessary for all lenses. It is typically recommended for lenses with higher refractive indexes, such as those made of high-index plastic or polycarbonate, as they tend to reflect more light. However, it can also be helpful for other types of lenses, such as those made of glass or standard plastic.

How do I care for and maintain anti-reflective coating?

To properly care for anti-reflective coating, it is important to clean your lenses regularly with a microfiber cloth and a mild, non-abrasive cleaning solution. Avoid using harsh chemicals or abrasive materials that can damage the coating. Additionally, be sure to handle your glasses with care and avoid placing them face down on hard surfaces to prevent scratches on the coating.

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