Interference in Thin Films

But yes, you can use trigonometry to find the wavelength.In summary, the conversation discussed a problem with interference in thin films and a worked solution was provided. It was also mentioned that 2t is related to the wavelength and can be used to find the wavelength using trigonometry.
  • #1
killerfish
16
0
Hi guys,

i have problem with Interference in Thin Films, i tried worked the solution not sure it is correct. Hope someone can help me check? Also there is some part on the topic i don't quite follow, 2t is the extra distance traveled inside the film, then is 2t is also rough estimate of wavelenth?


Homework Statement


A soap bubble (n = 1.33) is floating in air. If the thickness of the bubble wall is 115 nm,
what is the wavelength of the light that is most strongly reflected?


The Attempt at a Solution



the worked solution by me is in attachment.

dddd.JPG



Thank you.
 
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  • #2
After a quick look through, it looks fine to me.

Also, 2t is related to the wavelength from the equation you just worked out. It is more directly related to the wavelength of the light inside of medium, n=1.33. But not exactly sure what you are asking.
 
  • #3
sry for the late reply...

1. for example, if the system give destructive result, i should sub in (m + 1/2)[tex]\lambda[/tex]n into [tex]\Delta[/tex] at the third line of equation ?

2. and you mentioned the 2t is relate to the wavelength, then we actually can use that to find the wavelength entered into the thin film using simple trigo rule?
 
Last edited:
  • #4
1. Yes, for destructive interference the path length difference needs to be that.

2. You already solved it, so not sure what else you are trying to do here.
 
  • #5


Hello,

Interference in thin films is a fascinating phenomenon that occurs when light waves interact with a thin layer of material, such as a soap bubble. In this case, the thickness of the bubble wall is an important factor in determining the wavelength of the light that is most strongly reflected.

Your attempt at a solution seems to be on the right track. The equation you used, 2nt = mλ, is known as the thin film interference equation and is commonly used to calculate the wavelength of light reflected from a thin film. In this equation, 2t represents the extra distance traveled inside the film, and m is the order of the interference pattern. In this case, m = 1 since we are looking for the first order maximum.

However, 2t is not an estimate of the wavelength. It is the actual distance traveled inside the film, which is equal to the thickness of the film. So in this problem, the thickness of the bubble wall (115 nm) is equal to 2t. To find the wavelength, we rearrange the equation to solve for λ, which gives us λ = 2nt/m. Plugging in the values, we get λ = 2(1.33)(115 nm)/1 = 306.7 nm.

I hope this helps clarify any confusion you may have had. Good luck with your studies!
 

1. What is interference in thin films?

Interference in thin films is a phenomenon that occurs when light waves reflect off of two parallel surfaces with a small gap in between. This results in constructive and destructive interference, leading to the appearance of different colors depending on the thickness of the film.

2. What causes interference in thin films?

Interference in thin films is caused by the interaction of light waves with the reflecting surfaces of the film. When light waves reflect off of the top and bottom surfaces of the film, they interfere with each other, resulting in the observed colors.

3. How is the thickness of a thin film related to interference?

The thickness of a thin film is directly related to interference. As the thickness of the film changes, the path difference of the reflected light waves also changes, resulting in different interference patterns and colors.

4. What are some applications of interference in thin films?

Interference in thin films is used in many practical applications, such as anti-reflective coatings on glasses and camera lenses, thin film solar cells, and optical filters for color separation and enhancement in photography and displays.

5. How does the refractive index of a thin film affect interference?

The refractive index of a thin film plays a significant role in interference. A higher refractive index leads to a larger phase shift of the reflected light waves, resulting in a greater change in the interference pattern and colors.

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