Problem interpreting this interference question

[Zomboy]

1. Homework Statement

"A thin piece of metal foil of thickness 0.0700mm separates one end of two pieces of optically flat glass. The top sheet is 12.0cm long. Light of wavelength 529nm is normally incident on the glass. How many interference fringes are observed per cm in the reflected light?"

I don't really understand this question. I'm amusing that the 12cm glass pane is placed (possibly end on) on top of the second (infinitely large) pane, separated by an infinitely large sheet of (opaque/reflective) thin metal foil...

If someone could decode this question for me it would be much appreciated :)

 

[vela]

Like you, I couldn't make sense of it, but gneill explained it:

Two flat glass plates, one end of the pair is separated by a distance of 0.0700 mm. Thus they form a wedge. Interference will ensue...

 

[Zomboy]

That makes so much sense. Sometimes when tackling some of these questions I feel like a 3yr old playing with a bunch of shaped blocks trying to cram a stupid square one into that smug *** circular hole. Not my finest moment.