When an electron tunnels from one place to another, does in happen instantaneously, or does it require a finite amount of time? Can things other than electrons tunnel?
Asked by: Phil Reedy
Well, there is a nice piece of work done by Markus Buettiker
from Geneva (CH) concerning the travel time of tunneling
electrons. He has a web page where you can find some
For the second part of the question, photons can tunnel
as well. There is a nice experiment call Newton's experiment
which demonstrate the tunneling effect of photons:
You launch a laser beam on a prism such that a total reflection
occurs (that means that the angle of incidence respect to the normal
of the hypotenuse should be greater than the critical angle of
the media). In this configuration no light is transmitted,
all the intensity is reflected. now, if you approach very close
a second prism towards the hypotenuse of the first one,
without touching it you will frustrate the total reflection
and a beam will be transmitted to the second prism,
though there is no light between the two hypotenuse.
I don't want to go into detail, but the
phenomena can be explained by Maxwell's equation and
Actually a lot of research is done on this field, namely in
Scanning Near-Field Optical Microscopy (SNOM) which uses
the tunneling of photons .
(see for instance: http://monet.physik.unibas.ch/snom/)
Answered by: Alex, Ph.D Physics
'There comes a time when the mind takes a higher plane of knowledge but can never prove how it got there. All great discoveries have involved such a leap. The important thing is not to stop questioning.'