I heard somewhere that when a electron or photon tunnels through a potential barrier, it disappears and reappears on the other side, is this true?

Hm, it has a probability of being detected at either side of the barrier but not within the barrier. I'm not sure if you want to try to explain how that would look using classical particles...

I heard somewhere that when a electron or photon tunnels through a potential barrier, it disappears and reappears on the other side, is this true?

 

The particle has a probability of being on the other side of the barrier, even if its energy is smaller than the height of the barrier. Since it could not (classically) jump over the barrier, we describe it as tunneling through the barrier.

I heard somewhere that when a electron or photon tunnels through a potential barrier, it disappears and reappears on the other side, is this true?

 

It only appears but does not disappears. Mathematically it means the propability to find a particle behind a barier is a growing function of time.

It doesnt disappear as such....the proton would move closer to the barrier and then just seem to pass through it is probably the easiest way to visualise it. QM tunnelling is very important...especially in steller fusion (i.e. powering the stars)