Instructions: Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
Input: Convex lenses are thicker in the middle than at the edges so they cause rays of light to converge, or meet, at a point called focus.
Output:
Convex lenses are thicker in the middle than at the edges so they cause rays of light to converge, or meet, at a point called what?