Thin film interference Definition and 69 Threads

Good day! Sorry for my bad level of English, but I got a question about the interference of light in the case of Newton's rings. We know that If light rays fall on an installation consisting of a lens and a reflecting plate perpendicular to the surface of the lens, the interference pattern looks...

So, what I do not understand 1st and foremost is, when they say "see the film", does the light have to be reflected from the film or can I consider refraction of light through thin film also a case using which image can be formed? To be honest, I have solved this question before, but the problem...

I know that every time that light goes from traveling through a medium with lower refractive index to one with a higher refractive index the reflected light undergoes a ##\frac{\lambda}{2}## phase change. Since this happens both at the air-plate and plate-glass interfaces we have that the phase...

I have a monolayer of zeolite crystals on glass with the thickness of the zeolites about 800nm. When I look at the reflection of fluorescent light bulbs on this monolayer, the reflection is white except at specific angles. At around 45 deg, the colour appears red/magenta and at a lower angle...

First image showing script and plot Second image where all I have done is slightly change the thickness and now the plot looks very weird. Final image showing the kind of plot I am expecting. Am I just doing something stupid as I can't see what is wrong/different between my equations and the...

How do I work out what m value (0, 1/2, 1 etc) to put in the thin film interference equations like 2nt = (m + 1/2)*lambda? Does it depend if it's constructive or destructive? Could someone help explain, thanks!

Homework Statement Between two pieces of glass (##n_1=1.70##), there is a thin film of water (##n_2=1.33## and width ##d=1 \mu m##). If there is normal-incidence of white light on the water surface, find: (a) which wavelenghts can be seen in the light transmitted (answer: 667 nm,533 nm,444 nm...

Homework Statement You are working with the mineral fluorite (CaF2, n=1.43) and have a sample that is coated with a layer of liquid 158 nm thick. For various wavelengths of visible light incident normal to the surface of the liquid, you observe very strong reflection for green light (λ = 510...

Homework Statement A total of 31 bright and 31 dark Newton's rings (not counting the dark spot at the center) are observed when 550-nm light falls normally on a planoconvex lens resting on a flat glass surface. How much thicker is the center than the edges? Homework Equations 2t = mλ 2t =...

Homework Statement A uniform film of TiO2, 1036 nm thick and having index of refraction 2.62, is spread uniformly over the surface of crown glass of refractive index 1.52. Light of wavelength 515 nm falls at normal incidence onto the film from air. You want to increase the thickness of this...

Homework Statement A transparent film( n = 1.45) is placed on a glass surface( n = 1.14) and is illuminated by light ( incidence angle α = 60°. What is the minimum thickness d1 of film such that reflection of light with λ is minimized, while if the thickness is d2 then with the same λ the...

Homework Statement An oil tanker spills a large amount of oil (n =1.47) into the sea (n = 1.33). a) If you look down onto the oil spill from overhead, what predominant wavelength of light do you see at a point where the oil is 390 nm thick? What color is the light? b) In the water transmitted...

Homework Statement A researcher measures the thickness of a layer of benzene (n = 1.50) floating on water by shining monochromatic light onto the film and varying the wavelength of the light. She finds that light of wavelength 565nm is reflected most strongly from the film. What does she...

Homework Statement Two glass plaques of length 10.0 cm osculate, on one end, and are separated by a wire of diameter d = 0.0500 mm on the other. Light with two wavelengths (400 nm & 600 nm) falls on one of them, and we can see it gets reflected. At which distance from the point of contact...

Hi, in every explanation of thin film interference I came across, little or nothing is said as to why the layer of transparent material creating the effect should be thin. What would go wrong if that is not the case? I'm asking because it seems to me that, in principle, the mathematic...

Homework Statement I am working on a thin film interference problem where i have to find the phase difference. What is the relationship between external/internal reflection and the thin film interferenceHomework Equations for external: [/B] for internal: The Attempt at a Solution So far i...

If the equation for phase difference, 2(pi)(path difference/wavelength) gave you a value like 12.25pi would that be the phase difference or would it be .25pi?

Homework Statement A coating of n1 = 1.27 material is to be added to n2 = 1.50 glass, in order to make it "irridescent." a) What is the thinnest layer of material which will have a reflection maximum for normal-incidence light at BOTH 400 and 600 nm (vacuum) wavelength? b) This thickness will...

Hi, I actually have two questions that are somewhat related so I am including them in one post. I add much more detail about the system then probably necessary because I'd like to see if I have a correct understanding of how the system works in addition to the question itself. Please bear with...

Homework Statement Light of wavelength 550 nm in air is normally incident on a glass plate (n=1.5) whose thickness is 1.1 X 10^-5 m. (a) What is the thickness of the glass expressed in terms of the wavelength of light in glass?(b) How many reflected waves will experience the 180 degree phase...

Trying to get my head around constructive/destructive interference in thin film optics. The book does a good job of throwing formulas at you but I want some intuition. If we shine a laser with λ = 600 nm on a thin film of a material with refractive index 1.5, at what thicknesses will we get...

How do i demonstrate thin film interference with microscope slides? Textbook questions all mention that you will get parallel fringes when you put a hair between two microscope slides. However, i have tried doing so, but don't get the parallel fringes. I used a red laser pointer, and a...

Homework Statement A lens (##\mu##=1.5) is coated with a thin film of refractive index 1.2 in order to reduce the reflection from the surface at ##\lambda=480 nm##. Find the minimum thickness of the film which will minimize the intensity of reflected. [Assume near normal incidence]Homework...

Thin Film Interference Problem: A hair is placed at the edge... Homework Statement Thin Film Interference Problem: A hair is placed at the edge between two 10.0 cm glass plates of n= 1.52. Light of 400 nm wavelength shines on the glass and an interference pattern is formed. If the...

Homework Statement Light strikes two plane sheets of glass with a thin air space between them as shown. If the light has a wavelength of 580 nm and the air space between the glass has a thickness of 870 nm, predict whether the reflected light as demonstrated by rays A and B will cancel or...

Homework Statement White light is sent downward onto a horizontal thin film that is sandwiched between two materials. The indexes of refraction are 1.80 for the top material, 1.68 for the thin film, and 1.50 for the bottom material. The film thickness is 5.24*10^-7 m. (a) Of the visible...

Homework Statement A thin layer of water (n=1.33) is surrounded by air what wavelength of light will not be transmitted through the water at the point where the water is 113 nm thick? The Attempt at a Solution - In phase - Path difference of 2T. - Constructive Interference I just...

Hello, I am having some difficulties understanding this concept. It seems like wikipedia and my notes/teacher contradict each other According to my equation sheet, the equation for dark spots is 2nt = mλ and for bright spots is 2nt = (m + 0.5)λ. However, if a phase shift of 180 degrees occurs...

Homework Statement A very thin sheet of plastic (n=1.70) covers one slit of a double-slit apparatus illuminated by 630 nm light. The center point on the screen, instead of being a maximum, is dark. What is the (minimum) thickness of the plastic? Homework Equations Constructive...

I put together this little movie as (hopefully) the first in a series. http://www.youtube.com/watch?v=xjMjWtntm9k" My target audience is a second semester class of physics students that have already had a lectures in basic wave optics. When I give this URL to my students, it's with the...

Look at the picture below, I have to prove that the optical path length difference is \Delta=n(BC+CD)-BE=2nd\cos(r) [PLAIN]http://img200.imageshack.us/img200/2271/schermata082455775alle1.th.png The problem is just how to get 2nd\cos(r) I actually don't have any idea :\ I have...

Hello, I am trying to understand thin film (in air) interference but I have a problem: I know we have destructive interference when \delta=(2m+1)\pi. Now i can try to calculate the thickness of the film to get it, so since \delta =\frac{4nt\pi}{\lambda} - \pi where t is the thickness...

Homework Statement A piece of paper of thickness 15 * 10^-6 m is used to create an air wedge between 2 glass slides that are 7.25 cm long. If the wavelength of the light being used is 595 nm, how many interference fringes are counted across the entire pattern? Homework Equations delta...

1. Calculate the minimum thickness of the film for which the intensity of the reflected red ray is near zero. (This is AP Physics B 2010 (c)ii.) I found the wavelength in the film to be 4.81x10-7 m nf=1.382. 2L=mλ (destructive interference) The Attempt at a Solution My first attempt yielded a...

Homework Statement A pair of very flat glass plates, 7.41 cm long, touch at one end and are separated at the other end by a small piece of 44 gauge copper wire, 5.08×10−5 m in diameter. An air wedge is formed between the glass plates by this supporting wire. Light of wavelength 631 nm...

I am looking over thin film interference and am having some difficulty understanding when to know if a reflected ray will be 180 degrees out of phase or in phase. I know that a ray reflecting off a medium with a higher index of refraction will have a 180 degree phase change; and that a ray...

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...

Homework Statement So I have a similar situation with the traditional Newton rings. Instead of having however a convex lens, I have a (partial) spherical surface with height d with sitting on top of a thin film of thickness t, with d >>> t, and refractive index n and below the thin film is a...

Homework Statement [PLAIN]http://img403.imageshack.us/img403/2696/33095583.jpg The attempt at a solution I simply took 425 nm and divided it by 4 by using the destructive reflection from thin film. I got 106 nm as my answer, which is c. Is this correct?

Hi, I'm a high school physics student and I'm having a lot of trouble with thin film interference Homework Statement A thin layer of oil (noil=1.25) is floating on water (n=1.33). How thick is the oil in the region that strongly reflects green light (λ=556nm)? Homework Equations noil/nwater...

Homework Statement Light of wavelength \lambda = 500nm, produced by an extended source, is incident at an angle of \phi= 30 degrees from the normal upon a dielectric film of refractive index, n=2, supported on a solid planar substrate. Reflectivity minima are observed to have an angular...

I've learned that when a wave is partially transmitted and partially reflected, it loses some of it's amplitude in order to conserve energy. How then, in thin film interference, can one wave produce complete destructive interference with the other if it has been partially transmitted? Wouldn't...

Homework Statement What is the thinnest film of a coating with n = 1.43 on glass (n=1.52) for which destructive interference of the red component (660 nm) of an incident white light beam in air can take place by reflection? Homework Equations 2t = m*lambda? The Attempt at a...

1. The problem statement: A wavelength (λ)550 nm light ray traveling thru a viscous medium n1= 1.46 strikes a a crystal n3=1.5 protected by a film n2=1.25. [b]2. Relevant equation: How can I determine the min thickness of the antireflective coating used to minimize the reflection of...

Homework Statement Question: A soap bubble of index of refraction 1.48 strongly reflects both the red and the green components of white light. What film thickness allows this to happen? (In air, the wavelength of red light is 716 nm, of green light 511.429 nm.) n = 1.48 \lambda(r) =...

Not really a homework problem. Just wanted to know: When light moves from a medium of lower index of refraction to that of a higher index of refraction, the reflected ray suffers a phase change. (Thin film interference) But the other way round, this doesn't happen. This can be shown by...

Homework Statement The thin film is of two glass with air in the middle. refractive index of... air: n=1.0003 glass: n=1.5 lamba=632.8nm Q1.) Calculate optimum thickness of the film (for 1st order interference) Q2.) Why does the distance between interference fringe beome longer...

While completing my problem set for this chapter, I came across 5 problems I could not solve. I thought it might be rather annoying if I posted six posts, so I'm putting all my work and such here. I don't expect one person to try to help me with all of them, just one or two at a time will do...

Homework Statement A transparent oil with an index of refraction of 1.25 spills on the surface of the water (n=1.33), producing a maximum of reflection with incident orange light (\lambda = 602nm in air.) Determine the lowest possible thickness (in nm) of the oil slick.Homework Equations...

I don't have a particular homework inquiry to ask, just some questions I have about thin-film interference and its related equations. I was told by my instructor to learn these concepts on my own and I am just having a few problems I want to clarify. 1) Equations related to thin-film...