Observer's Dilemma

Pavitra Kanetkar |

 In Young's Double Slit experiment, Interference pattern depends on the position of the detector.

Here are the experiment data results, A single photon is sent at a time and next is sent when previous photon hits the screen.

1. If a detector is placed just after the source then observer will not be able to find the slit in which electron is going to pass so the interference pattern will appear on the screen.

Interference pattern (Fringes) appears because electron acts as a wave and passes through both the slits.



2. If a detector is placed just before the slits then observer will be able to find the 'which way' path of the electron and interference pattern will not appear on the screen.

We will see the two fringe pattern on the screen.


 

3. If a detector is placed just after the slits then observer will be able to find the 'which way' path of the electron and interference pattern will not appear on the screen.

You must think, if interference pattern will not appear then two fringes pattern will appear but experimental data shows neither appear. In this case, A blob pattern appears because the wave function collapse happens when electron has already passed the slits.



4.  If a detector is placed just before the screen and even if observer is not able to find the 'which way' path of the electron still interference pattern will not appear on the screen because wave function collapses just before hitting the screen. In this case, A blob pattern appears because the wave function collapse happens when electron has already passed the slits.


 

5. A screen acts as a detector so the wave function is collapsed on the screen. Placing a detector before screen is same as placing a screen before screen. Detector does not show you any pattern but a screen does. So Interference pattern is still there at the first detector which is placed after the slits, just you can't see it, same as it is there at the screen if no detector is placed before screen.

 Note :

Simple definition of wave function collapse is initially a wave function is superposition of several eigen states which reduces to single eigen state.


Comments

Post a Comment

Popular posts from this blog

Wheeler's Delayed-Choice Experiment

Pavitra Kanetkar |
Image
Wheeler's delayed choice experiment is a thought experiment in quantum physics that was proposed by physicist John Archibald Wheeler in 1978. The experiment is designed to explore the nature of wave-particle duality and the role of observation in quantum measurements. Case : A The experiment involves a setup where a beam of photons is directed towards a beam splitter at lower left corner. There is 50-50 probability that the photons will be transmitted (pass through straight direction to the bottom right mirror) or reflected (sent to the top left mirror).  At beam splitter, if photon is transmitted, it is sent to the mirror which is placed at the lower right corner. It will reflect the photon to the top of the apparatus where screen - A is placed At beam splitter, if photon is reflected to the top left mirror, it will reflect the photon to the top right where screen - B is placed.  In both cases we will find the path of the photon. Either it follows clockwise route or anti cl...
Read more

How Newton Beat 1500 Years of Pi Calculations — In Just Hours

Pavitra Kanetkar |
Image
  For over a thousand years, mathematicians struggled to calculate the digits of π (pi) , the mysterious number that relates a circle's circumference to its diameter. The ancient Greek genius Archimedes had started it all around 250 BC by drawing polygons inside and outside a circle, calculating their perimeters to trap π between two values. This method was ingenious but painfully slow. For centuries, this "polygon method" was the best humanity had — with later minds like Ludolph van Ceulen calculating π to 35 digits using thousands of polygon sides. He dedicated his entire life to this — so much that his digits were engraved on his tombstone . Then along came a man named Isaac Newton .   The Calculus Revolution Newton didn’t need thousands of polygon sides. He had something far more powerful: calculus — and a brilliant idea. He thought: Why not express the geometry of the circle in a completely different language? Not with shapes, but with algebra and infinit...
Read more

Future Visibility Limit

Pavitra Kanetkar |
  1. The future visibility limit is 62 billion light-years. This does NOT mean that objects at this distance emit photons toward us now, and that those photons will reach us sometime in the future. 2. Any object farther than 16.5 billion light-years emits photons toward us now, but those photons will never reach us, even if we wait for an infinite amount of time. 3. So what is 62 billion light-years? Well, it is the radius of a sphere from HERE NOW. Those objects within this sphere, whose photons we have not yet received, emitted light in the past when they were within 16.5 billion light-years of us. These photons are still on their way, and when they reach us in the future, we will be able to see those objects. 4. We will only be able to see objects in the future that are currently within the 62 billion light-years radius, and whose photons have already entered the 16.5 billion light-years radius. 5. We will never receive photons from these objects that haven't yet...
Read more