Interference Definition and 999 Threads

Hi PF I wonder how qubits interfere in interferometers when they are not in pure states. Let us take qubits with density matrix = Id/2. There lay at the center of the Bloch sphere. Half of them can travel unchanged through the left arm. In the other arm they become ##UP_Z##. Then there is...

Hi all, I have a small misunderstanding about the energy conservation in diffraction from 2 slits. First, I understand the energy conservation of interference from 2 slits. If intensity from each slit is I, then I have intensity of 2I after slits plane. Interference is given by: So at bright...

This is my first post here, so hello to all. I came here looking for advice. I am far for considering myself even a newbie regarding physics, I have huge gaps in knowledge. However, as I happen to "know my way around computers", I am helping my friend in her art project. Sparing you the...

If I have 2 identical laser pointers, is it possible for me to point them both at the same spot on a wall and see no light at all due to complete destructive interference?

Bear in mind that I am talking about monochromatic light. I looked into this subject and the thing that many say is that when we have thick films, the two reflected waves are not considered to be coherent any more(and something about coherence length). I can't see why this is the case(and I have...

Hello, if have a question concerning the difference between " interference" and "diffraction". Interference can be created, by superposition of countable many wavefields. So if I have a countable amount of wave sources, then the superposition can be called an interference. In contrary, for...

Hi PhysicsForums, Here's a thin film interference question I'm having problems with. An oil film (n=1.50) floats on a water body (n=1.33) in an air environment. Normal incident white light is reflected by the oil film. But in the spectrum of reflected light, 500nm and 700nm light are missing...

Hello! I would be very happy if you could lend me a helping hand with the following problem. :) 1. Homework Statement We know that a CD is read with a laser with a wavelenght of λ = 1 μm. a) Estimate the data stored on the CD. b) We know that the CD contains 80 minutes of sound. How fast is it...

Hello guys, Suppose a process 1+2--->3+4 proceeds thru 3 different intermediate particles and has 3 Feynman diagrams. When we compute the probability then what does the cross terms( interference ) mean? and do we have to always compute the cross terms? What I mean is that when you have 3...

I am not sure if this is the correct place to put this question, as it is rather straight forward. But anyway, does anyone know if/where I could find a scanned (or otherwise copied) copy of Young's original experiment (or his paper(s) on it)? I am doing a project, that amounts to some...

Third question about wave optics in two days, hope it's not too much. When we look at the intensity of light on the screen in a double-slit interference experiment (assuming negligible diffraction), we find something like this : When we look at the intensity of light on screen in a...

Homework Statement A thin piece of metal foil of thickness 0.0700 mm separates one end of two pieces of optically flat glass. The top sheet of glass is 12.0 cm long. Light of wavelength 529 nm is normally incident on the glass. How many interference fringes are observed per cm in the reflected...

I recently learned about the so called "diffraction" grating. In most textbooks I have seen, it is described as multiple slits setup, with really narrow slits. It is sometimes said that the width of the slits is much less than the wavelength of the light going through it. Where is the...

In the double-slit diffraction experiment, two interferences are observed simultaneously : diffraction interference from each single-slit, and double-slit interference (where in the double-slit interference, diffraction is ignored because we considered theoretical slits way smaller than...

Homework Statement A sheet of glass (nglass = 1.5) is coated with a 95.6-nm-thick layer of magnesium fluoride (ncoating = 1.38) to prevent reflection in the visible spectrum. Assume the incoming light is normal to the surface. What is the longest wavelength of light strongly reflected from this...

Homework Statement Monochromatic light of wavelength 463 nm from a distant source passes through a slit that is 0.0350 mm wide. In the resulting diffraction pattern, the intensity at the center of the central maximum (θ = 0∘) is 9.20*10-5W/m2 . What is the intensity at a point on the screen...

< Mentor Note -- thread moved to HH from the technical physics forums, so no HH Template is shown > Hi guys, I have a question here which I'm struggling to do and perhaps you could help ; Monochromatic electromagnetic radiation with wavelength λ from a distant source passes through a slit. The...

what does it mean by localisation of fringes?

Homework Statement Homework Equations I α A2 The Attempt at a Solution My teacher told us that if the source is a light source, then the answer would be B, why? Why would the intensity be the same for each maxima? And zero intensity when at minima? I thought its amplitude will decrease as it...

Homework Statement In a diffraction experiment in which electrons of kinetic energy 110 eV are scattered from a crystal, a first maximum in the intensity of the scattered electrons occurs at an angle θ=10.7 a) How many peaks will there be in the interference pattern? b) What is the spacing...

Where do the energy go in a pair of photons that are annihilating each other exactly? What happens when they collide with something that absorbs photons like an electron? (I think electron can absorb the e. in a photon to jump into a higher level) Would this light wave become undetectable like...

Pretend we have a multi-slitted grating whose slits are infinitesimally small. We On each slit is a detector. If we shine (UPDATE) light monochromatic light through the grating, what distribution pattern occurs on the screen past the grating? I understand the train of thought to a slight...

Homework Statement A thin film with an index of refraction of 1.60 is placed in one of the beams of a Michelson interferometer. If this causes a shift of 8 bright fringes in the pattern produced by light of wavelength 580 nm, what is the thickness of the film?1.5 µm 2.9 µm 3.9 µm 7.7 µm 16...

My textbook says that the trough of the electromagnetic wave cancels out when it meets a crest. Okay, that makes sense, but if the crest is the actual photon/wave of energy, what is this trough that can cancel out the energy? It seems to mean that there are "negative energy photons" in between...

When EM waves interfere, what happens to the energy?

So, I'm about to take an Optics exam, and while I can easily do most of the last years' exam problems, there are some which I cannot solve for different reasons (perhaps some gross oversight?). Yesterday I stumbled upon this: 1. Homework Statement (my own translation from Catalan) We have a...

Homework Statement Two sound sources are coherent and in phase. Is there constructive or destructive interference at the midpoint between the speakers? Homework Equations Generally, there is constructive interference whenever the path-length difference is an integer times the wavelength...

A string has one end tied to a wave generator, and the other tied to a fixed position,. It takes the wave 0.10 seconds to travel 4.5m. Withing the same distance there are 3 complete loops. Find the frequency of the source. Pretty generic question. But I keep getting stuck at trying to find the...

Why does the interference pattern of the photon go away when one places a convex lens far away from the two slit to only show a particle build up of the two slits? This is the experimental set up, the lens is in place far after the photons pass through the two slit and hit the back wall in a...

In afshar's experiment, it shows that the single photon goes through only one of the slits and produces an interference pattern. How is this possible? In this experiment, do we really know which slit the photon went through?

[Mentor's note: This thread was split out from another longer one because it is an interesting topic in its own right] Something that I've been confused about when it comes to interference between photons is the distinction between two different quantities that can interfere constructively or...

I suppose a related question is in regard to the fundamental nature of quantum superposition. Does any system in superposition "necessarily" demonstrate interference on a macroscopic scale?

I have been trying to mathematically explain the empirical result that putting orthogonal polarisers (quarter-wave plates) behind the two slits of a double-slit setup will erase the interference pattern. The trouble is, my analysis predicts an interference pattern. I must have made a silly...

Homework Statement Homework Equations dsinθ =nλ The Attempt at a Solution I don't understand why an interference pattern will only be observed along XY only. Why don't the waves intersect along RS. Does it have something to do with R being the midpoint of PQ?

Figure 35-57 shows an optical fiber in which a central plastic core of index of refraction n1  1.58 is surrounded by a plastic sheath of index of refraction n2  1.53. Light can travel along different paths within the central core, leading to different travel times through the fiber.This causes...

In a double-slit experiment, the distance between slits is 5.0mm and the slits are 1.0m from the screen. Two interference patterns can be seen on the screen: one due to light of wavelength 480nm, and the other due to light of wavelength 600nm. What is the separation on the screen between the...

Hello all, The following question is related to digital communication systems. I am studying two systems operating at the same time and on the same frequency. Each system consists of one transmitter and one receiver. However, one of them, let us say system 1, is using channel coding with code...

Consider the situation where the electrons in an antenna accelerate from the top of the antenna to the bottom of the antenna once, what would the interference pattern look like if the electromagnetic radiation from the antenna were passed through a double slit apparatus of an appropriate size? I...

Homework Statement One microscope slide is placed on top of another with their left edges in contact and a human hair under the right edge of the upper slide. As a result, a wedge of air exists between the slides. An interference pattern results when monochromatic light is incident on the...

Homework Statement A parallel beam of light of wavelength ##\lambda## is incident normally on a thin polymer film with air on both sides. If the film has a refractive index ##n>1##, then, for what value of the thickness, can second order bright fringes be observed in reflection? Homework...

Homework Statement https://fbcdn-sphotos-h-a.akamaihd.net/hphotos-ak-xft1/v/t1.0-9/11161364_10206082495958864_2429387894279713850_n.jpg?oh=40982e4e4e7647918991060b6f630acc&oe=55C1808A&__gda__=1439347320_8abd4b5ce66baee04bbc345aef15ec68 In terms of the wavelength of the light λ, what is the...

Homework Statement A monochromatic light source is used with a double slit to create an interference pattern on a screen that is 2.00 meters away. If the 2nd bright spot is observed 8.73 mm above the central maximum, can the small angle approximation be used? Show and/or explain your reasoning...

I had a physics course a few years back that touched on constructive and destructive waves and only today did i notice this phenomenon with my speakers. I was curious about the theory behind this particular scenario in my room. I have one of those mobile speakers, a bose soundlink II. It has 4...

With laser pointers being so ubiquitous, everyone is familiar with the sight of interference patterns on paper, ground glass and other surfaces (not to mention more subtle experiments like this one): Quantum Eraser -- which has been discussed recently in other threads. We take it for granted...

Homework Statement Two loudspeakers on elevated platforms are at opposite ends of a field. Each broadcasts equally in all directions. At the halfway point, the intensity is 74.1dB. What is the sound intensity level at a point one-quarter of the way from one speaker to the other along the line...

Homework Statement Two (left) circularly polarized monochromatic plane waves S2 and S3 arrive at the xy plane with an incidence angle θ (see figure). Find the intensity of the light projected in the xy plane. (Nevermind S1, it is only mentioned in another part of the problem) Homework...

1. Homework Statement If the optical path diff between two light waves is lambda/2 will they always interfere destructively? if this in true then wherever one wave undergoes aphase change of pi at one surface and the second wave does not then these two will always interfere destructively...

Could someone please explain this question to me I'll include what I thought the answer was and the actual SQA answers. Please can you read my answer just to see what I'm doing wrong and what I don't understand It's from the 2009 past paper AH physics Thanks so much I really appreciate any...

The prevailing wisdom is that coiling excess signal cable under an MRI magnet for storage in a figure-8 configuration will reduce or eliminate induced noise onto the cable from the pulsing fields from gradient coils. I am starting to doubt this, however. A quick diagram of a figure-8 looped...

Upon using Thomas Young's double-slit experiment to obtain measurements, the following data were obtained. Use the data to determine the wavelength of light being used to create the interference pattern. Do this in three different ways. - The angle to the eighth maximum is 1.12 deg. - The...