# Effect of photon detection mid-way between (double) slit and screen

1. Feb 27, 2013

### San K

In a single particle double slit (self-interference) experiment:

the which-way information is got by having the detection instrument (or at-least part of the instrumentation) right next to the slits.

To make it easier, Let's assume the following x-coordinates:

at source of photon x = 0
slits are at say x = 10
the final screen (i.e. where the pattern is formed) is at, say, x = 20

The question is:

1. can we detect the photon at x = 15? (i.e. somewhere between the slits and the screen)

if so,

2. would it's location (i.e y-coordinates at x =15) be consistent with self-interference of the wave function? i.e. show an interference pattern at x = 15? and if we were to let it proceed further (after detection) would it just proceed in a straight line and show a blob at x = 20?

thus interference till the time the photon is not detected and no-interference after that for sometime.

i hope i have been able to explain the question accurately, else I will do so in my responses

Last edited: Feb 27, 2013
2. Feb 27, 2013

### Staff: Mentor

Re: effect of photon detection mid-way between (double) slit and scree

How is this different from just putting the screen at 15 instead of 20?

3. Feb 27, 2013

### San K

Re: effect of photon detection mid-way between (double) slit and scree

good question.

the detector allows the photon to carry/pass on its journey beyond 15

the screen ends the journey of the photon..... at the screen at 15

anyhow, i think you answered my question

Last edited: Feb 27, 2013