Why need a screen to display interference

[alkmini]

Homework Statement

why do we need a viewing screen in order to see interference patterns? why can we see interference patterns through our fingers when we look at a distant light source and we don't need a screen in that case?
what do we mean by visible light? can we see the wave itself, crests and toughs as we see in water waves? If we don't see it, is it because the wavelength is too small or because electromagnetic fields are invisible? if electric and magnetic fields are invisible then what are the light fringes in interference patterns?

Homework Equations

The Attempt at a Solution

 

[technician]

you are quite correct, it is not essential to have a viewing screen but if you want to make measurements of fringe separation, distance from double slits etc then you need to have the pattern visible on a screen of some sort.
The traditional school demonstration of Young's double slits experiment is done with a screen

 

[alkmini]

thanks a a lot