instruction:
Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
question:
A concave lens is thicker at the edges than it is in the middle.
answer:
What type of lens is thicker at the edges than it is in the middle?


question:
A volcano chain is formed by subduction of oceanic crust beneath a continental or oceanic plate.
answer:
What kind of chain is formed by subduction of oceanic crust beneath a continental or oceanic plate?


question:
Radio waves are the broad range of electromagnetic waves with the longest wavelengths and lowest frequencies.
answer:

What waves are the broad range of electromagnetic waves with the longest wavelengths and lowest frequencies?