Why does detecting which slit breaks the interference pattern?

[Milind_shyani]

Hi,
We all know that when we shoot electrons one by one on an apparatus having two slits then it forms a interference pattern. Means this implies that the electron passes through both the slits at the same time
Now when we keep a detector near the slits to watch the electrons than the electrons do not form an interference pattern why?
Is it beacuse that the detector while "watching" the electron disturbs its momentum or postion?

 

[FunkyDwarf]

Essentially. The uncertainty of QM stems from the nature of measurement, that you can't extract information from something without disturbting that state.

 

[malawi_glenn]

This implies that our classic understandig of nature breaks down at the microscopical level. A particle is not a small little ball, it is a wave package.
The same holds for the photom, in interference experiment, it behaves like a wave, in photoelectric effect, it behaves as a particle.

It think that it is things like this that makes physics very facinating!