"to what extent" vs. "to what level" [duplicate]
Solution 1:
"To what extent was the area flooded?" asks how much of the area was flooded.
"To what level was the area flooded?" asks how deep the water was.
The metaphoric usage would mean more or less the same thing:-
"To what extent have you studied physics?" asks how many topics you have studied in physics, or how long have you spent doing so.
"To what level have you studied physics?" asks how advanced your studies were.