Questions About the Double-slit Experiment

How far apart must the slits be? Does it matter?
Does the size of the slits matter?
Are there certain characteristics required of material the slits are made in? Like a certain density for example.
Why do our eyes seem to detect photons as single particles instead of waves?

Thanks in advance to anyone who has time to explain these to me.
Thank you! I have watched a dozen vids about this on youtube and the is by far the best one. One thing I failed to realize before is that the wave's interaction with the end screen also counts as an observation, which is explained in this video. Pretty cool!

We are Borg

Staff member
Yes the quantum world is insane when it comes to observations. Its very hard to understand and you need to rewatch it a few times because you will miss stuff the first time.