In modern physics, the double-slit experiment is a demonstration that light and matter can display characteristics of both classically defined waves and particles; moreover, it displays the fundamentally probabilistic nature of quantum mechanical phenomena. This type of experiment was first performed, using light, by Thomas Young in 1801, as a demonstration of the wave behavior of light. At that time it was thought that light consisted of either waves or particles. With the beginning of modern physics, about a hundred years later, it was realized that light could in fact show behavior characteristic of both waves and particles. In 1927, Davisson and Germer demonstrated that electrons show the same behavior, which was later extended to atoms and molecules. Thomas Young's experiment with light was part of classical physics long before the development of quantum mechanics and the concept of wave-particle duality. He believed it demonstrated that the wave theory of light was correct, and his experiment is sometimes referred to as Young's experiment or Young's slits.
The experiment belongs to a general class of "double path" experiments, in which a wave is split into two separate waves that later combine into a single wave. Changes in the path-lengths of both waves result in a phase shift, creating an interference pattern. Another version is the Mach–Zehnder interferometer, which splits the beam with a beam splitter.In the basic version of this experiment, a coherent light source, such as a laser beam, illuminates a plate pierced by two parallel slits, and the light passing through the slits is observed on a screen behind the plate. The wave nature of light causes the light waves passing through the two slits to interfere, producing bright and dark bands on the screen – a result that would not be expected if light consisted of classical particles. However, the light is always found to be absorbed at the screen at discrete points, as individual particles (not waves); the interference pattern appears via the varying density of these particle hits on the screen. Furthermore, versions of the experiment that include detectors at the slits find that each detected photon passes through one slit (as would a classical particle), and not through both slits (as would a wave). However, such experiments demonstrate that particles do not form the interference pattern if one detects which slit they pass through. These results demonstrate the principle of wave–particle duality.Other atomic-scale entities, such as electrons, are found to exhibit the same behavior when fired towards a double slit. Additionally, the detection of individual discrete impacts is observed to be inherently probabilistic, which is inexplicable using classical mechanics.The experiment can be done with entities much larger than electrons and photons, although it becomes more difficult as size increases. The largest entities for which the double-slit experiment has been performed were molecules that each comprised 2000 atoms (whose total mass was 25,000 atomic mass units).The double-slit experiment (and its variations) has become a classic for its clarity in expressing the central puzzles of quantum mechanics. Because it demonstrates the fundamental limitation of the ability of the observer to predict experimental results, Richard Feynman called it "a phenomenon which is impossible […] to explain in any classical way, and which has in it the heart of quantum mechanics. In reality, it contains the only mystery [of quantum mechanics]."
Following scenario:
One million entangled photon pairs are created and are sent to Alice's and Bob's laboratory such that Alice receives 1 million photons(or any other large number) of which each is entangled to one of the million photons Bob receives, their laboratories being at a distance to...
1. The statement, all variables and given/known data
Hi I'm doing this experiment where we need to find the wavelength of our laser light source. I am unsure what the variables IV and DV would be and the controlled variables? Also how will I make the graph? I'm in AS level so please don't make...
Homework Statement
A point light source is used in a Double Slit experiment. The light source contains two wavelengths(500nm and 600nm).
Separation of the two slits d=1mm. Two sets of interference fringes are formed on a screen. Find the angles θ where bright fringes are formed for both the...
In the double slit experiment, when you measure which slit your photon passes through, it will land in the corresponding location on the photosensitive film at the end of the apparatus. If, however, you don't measure which slit it goes through, an interference pattern will appear on the film...
Homework Statement
Consider a double slit experiment with a light source of 540nm. Slit separation is 4mm. A thin glass plate is placed in front of one of the slit,, resulting in each bright fringe moving to the location of the adjacent bright fringe. Find the minimum thickness of the glass...
My question is about the experiment in which detectors are used behind the slits to determine which slit the photon goes through. Specifically, it's about the detectors themselves. What I found is that these detectors are some kind of photoelectric detectors. My question is this. During the...
Homework Statement
Having recently completed an experiment on Young's double slit experiment for both high and low intensity light; I am having trouble writing conclusions in the report. In one part of the experiment I know I was firing only one photon at a time down the tube, and I achieved an...
From my shallow understanding, when we shoot a small amount of electrons through the slits while observing, the observation interfere with the electrons and the quantum system and thus collapse the wave function, making the electrons behave like a particle and form a 2-slit pattern on the...
I'd like to ask what exactly do the results of double slit experiment mean? I must confess that I've read about this mainly in New Age literature where it was used as a "proof" that our consciousness changes reality. I know that Physicists probably don't like such explanations :eek:
So I'd like...
When the slits are made narrower (but with same separation) why are more fringes produced? If the slits are narrower, less light enters, so less light interferes with each other, so lesser number of fringes should be produced, isn't it?
Hiya,
Another me trying to grasp some physical experiment. I'm working myself through a Dutch popular science book "Snaartheorie" (String Theory) by 'our' professor Marcel Vonk: it's meant to give the reader a maths-less impression of the theories behind string theory.
Vonk starts with an...
Might I be so bold as to ask a question about the "double slit experiment". Was wondering...have scientist ever considered...turning the observation on and off...? Is it even possible...? Experiment says...when observed...particles react one way...and when not observed...they react a different...
Homework Statement
For a question in a worksheet (the actual question is irrelevant), my physics teacher said, in the context of the Young double slit experiment with light, if you make one of the slits smaller, then the amplitude of light from that source will also decrease.
Is that true...
I know when they performed the famous double slits experiment they used either electrons, or photons.
I am trying to find out what is the largest size we could use (proton, molecule, etc) where the probability of wave-particle duality to occur in the experiment drops to something negligible...
Homework Statement
Laser light with a wavelength 633 nm is used to illuminate two slits separated by 0.125 mm. The width of each slit is 0.0150 mm. Assuming that only fringes between the first minima in the pattern are counted, how many bright fringes are visible?
lambda = 633nm
d = 0.125mm
w=...
For an electron can I not do the following to determine both the position and momentum? I take a screen with a small hole and I eventually make the hole smaller and smaller. Cathode rays emitted will hence get diffracted after passing through the hole making momentum more and more uncertain...
Homework Statement
A thin flake of mica (n=1.58) is used to cover one slit of a double-slit arrangement.The central point on the screen is occupied by the 7th brigth fringe.If lamda = 550nm, what is the thickness of the mica?
Homework Equations
path difference d=(n-1)*thickness
d=7*lamda...
Hello, All!
I'm writing a bit of fiction, and as a newcomer to the world of Quantum Physics, I thought I'd clarify a few concepts here, to avoid lapsing into technobabble. I'm trying to make something along the lines of the film Primer, which tries to incorporate as much realism as possible...
I was watching a video about the double slit experiment because I found it interesting, However, watching this vid raised more questions than it did answer. I would like to know why did the outcomes of the experiment only change when we observed it... wasn't the electron interacting with...
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...
Pretty obvious that measuring at the double slits neutralizes whatever action or reaction is creating the wave pattern. But why the quantum leap to assuming superposition?
What other configurations have been tested or were there just slits used? What about a round hole or holes, an “X” slit or...
In a double slit experiment (say, of electrons), when putting a detector to examine the passing of electrons through one slit, the wave pattern of the electrons disappears and instead the particle pattern appears. The classical explanation is that an electron exists both as a wave and as a...
Homework Statement
1. The distance between the 1st bright fringle and the 21st bright fringe in a Young's double slit arrangement was found to be 2.7 mm. The slit separation was 1 mm and the distance from the slits to the plane of the fringes was 25 cm. What was the wavelength of the light...
Hey guys the Idea of simulating the DSE with a program caught my interest but I just had a few questions regarding the DSE
Is there a function that models the probability of finding an electron at a certain point ONCE It's BEEN FIRED FROM AN ELECTRON GUN? like an amplitude function squared or...
I understand the experiment and the trigonometry involved except for one statement.
Why is BP-AP=BD in this diagram
http://www.citycollegiate.com/interference2.htm
How do you know this/ work it out.
Many thanks
sir, what if we use Heisenberg's uncertainty principle to explain double slit experiment?
i was reading about uncertainty principle for last few days n i was reading about double slit experiment and i realize that we can explain why we get electrons everywhere on the screen (getting...
I just thought about this one, suppose we have the classic double slit experiment setting, and we add near the holes in the slits a strong magnetic field, what will happen? what if the magnetic field was only on one slit? What if we put that magnetic field in place (2) instead of (1), would that...
http://www.pnas.org/content/109/24/9314.full
According to the experimenters they have found out which path the photon took and still observed the interference pattern. So they know that the particle went through the left or right slit but at the same time saw the interference pattern built up...
I don't know if you physicist out there knows it, but the statement that observing something changes its state is having a drastic impact on the less informed populace at wide.
An example, one of the most popular Quantum Physics video on youtube
<Link to video not acceptable under PF rules...
I have a question about how the double-slit-with-detector experiment works out with a beam of light.
(1) When you fire electrons through the double-slit apparatus, it creates an interference pattern on the screen. (2) When you place a detector at one of the slits, the interference pattern is...
In 2012, experimenters showed that when two entangled photons separate and when one goes through the double slit, we can tell which slit it went through and see that they still created an interference pattern because the photon that it was entangled to tells us which slit it went through. What...
In the double slit experiment, what is the position and momentum of an electron/photon?
Is the position of the electron/photon which slit it went through? And is the momentum of the electron/photon the wave like interference pattern detected on the detector screen?
Has the double slit experiment ever been performed 'in the round' ?
I mean within a circle, a fence, all around the source?
Electromagnetic radiation is promulgated in three dimensions, is it not?
To be fired like a bullet in one direction requires deliberate artificial constraint.
I'd have...
Homework Statement
In a Young's double slits experiment, a monochromatic light source of wavelength 700nm is used and the separation of the slits is 0.1mm. If 15 bright fringes are observed, what is the angle subtended by those fringes at the centre of the double slit?
A. 6.0°
B. 5.6°
C. 5.2°...
In one double slit experiment, one physicist placed a convex lens before the back screen detector. The individual photons passed through the double slit then through the lens. The individual photons then go through the focal point, then a good distance after they reach the focal point they hit...
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?
Homework Statement
A sheet of mica ( approximate 6-7 µm) covers one slit
of a double-slit apparatus and has a n= 1.582. There is a central maximum of 539 nm. What is the exact thickness of the sheet of mica?
Homework EquationsThe Attempt at a Solution
I think you can solve this with the...
I was wondering if the double slit experiment had been conducted in space away from interference from Earth's magnetic core/field. I know the scientific community would have considered all variables and would have set proper controls for this experiment but I am unable to find any notes on this...
Has the double slit experiment ever been performed with an adjacent reflection? With quantum weirdness I'm curious as to whether the reflection would give the same results as the actual apparatus as to which slit the particle wen through.
WARNING. I'm not a physicist! If there was a universe that only had 10000 photons and we observed all of them then ran the double slit experiment would we get a normal pattern or an interference pattern? If we observe a particle is that it forever in the universe that we happen to be running...
The results of the double slit experiment lead to the conclusion that a photon travels as a wave. Question 1: Is it possible to track the journey of the photon? It seems to me (correct me if I'm wrong) that from the moment we release the photon till contact with the detector we don't know what...
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...
Can someone please point me to an experiment (photons/electrons/whatever) where detectors were placed on both slits, this seems like a really big hole in the experiment if they stopped at having just the one detector. (Excuse the pun)
I am trying to understand the mathematics of quantum eraser experiments, in order to deepen my understanding of what is really happening. The paper I am currently working on is:
"A double-slit quantum eraser" by S. P. Walborn, M. O. Terra Cunha, S. Padua, and C. H. Monken (2001)
in which a...
May I ask about this configuration:
Let's say we install detectors on the slits so the detection at the screen will be 2 dots, one coming from slit A and one coming from slit B. No interference pattern.
We also set up the experiment so that there is not 1 observer but 2.
Observer A' is placed...
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...
I've been reading up a lot on the double slit experiment recently (and I'm no physicist at all). Although I haven't really seen the experiment done with my own eyes, from the demonstrations on youtube it seems as though the pattern when shining a laser through the slits is constant and solid...