Thin Film Interference Patterns

In summary, The conversation is about determining the thickness values at which destructive interference occurs in a setup where air is replaced with a liquid. The phase shift inside the wedge is 4pi times the thickness, and the type of interference is determined by the resultant phase shift of the two reflections.
  • #1
jegues
1,097
3

Homework Statement



See figure attached.

Homework Equations





The Attempt at a Solution



Not too sure how to do this one.

I tried thinking about what it was doing before the air was replaced with the liquid.

With air,

The first reflection would have no phase shift (glass index to air index), the second reflection would have a phase shift of pi (air index to glass index) so overall we a have a phase shift of pi.

How do I obtain an expression about the interference pattern from this?

With the liquid instead of the air, we will still have a phase change of pi but the wavelength will change since the index of the liquid is 4/3 not 1.

Any ideas?

Thanks again!
 

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  • #2
At what thickness values do you get destructive interference?

ehild
 
  • #3
ehild said:
At what thickness values do you get destructive interference?

ehild

I have no clue. How do I go about figuring that out? I thought the type of interference I had was determined by the resultant phase shift (if any) of the 2 reflections.

Can you explain?
 
  • #4
jegues said:
I thought the type of interference I had was determined by the resultant phase shift (if any) of the 2 reflections.

Yes, an the phase shift inside the wedge is 4pi times the thickness.

ehild
 
  • #5



Thin film interference patterns occur when light reflects off of a thin film with a different refractive index than the surrounding medium. This causes some of the light to reflect off the top surface of the film, while some of it travels through the film and reflects off the bottom surface. These two beams of light then interfere with each other, creating a pattern of bright and dark fringes. The equations used to describe this interference pattern depend on the thickness and refractive index of the film, as well as the angle of incidence and the wavelength of light. In this case, the liquid has a refractive index of 4/3, which will affect the phase shift and the wavelength of light. To obtain an expression for the interference pattern, you can use the equations for thin film interference, which take into account the change in phase and wavelength due to the different refractive index. It may also be helpful to consider the path difference between the two beams of light, as this will affect the interference pattern as well.
 

What is thin film interference?

Thin film interference is a phenomenon that occurs when light waves interact with a thin film of material. This interaction causes some wavelengths of light to be reflected and others to be transmitted, resulting in a pattern of light and dark areas known as interference fringes.

What causes thin film interference patterns?

Thin film interference patterns are caused by the difference in the refractive index of the thin film material and the surrounding medium. This creates a difference in the speed of light, causing the light waves to interfere with each other, resulting in the observed pattern.

How can thin film interference patterns be used in scientific research?

Thin film interference patterns can be used to study the properties of materials, such as their refractive index and thickness. They are also used in various optical devices, such as anti-reflective coatings and optical filters, and in the production of thin film technology, such as computer screens and solar cells.

What factors affect thin film interference patterns?

The thickness and refractive index of the thin film material, as well as the angle and wavelength of the incident light, can all affect the interference pattern. Additionally, the type of material, its surface quality and the surrounding medium can also influence the pattern.

How is thin film interference different from other types of interference?

Thin film interference is different from other types of interference, such as diffraction and double-slit interference, because it involves the interaction of light waves with a specific thickness of material. This results in a distinct pattern of light and dark areas, rather than the overlapping of multiple diffraction patterns.

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