Given the task definition, example input & output, solve the new input case.
Given a scientific passage and an answer, generate a question for the given answer.
Example: Passage: A frameshift mutation is a deletion or insertion of one or more nucleotides that changes the reading frame of the base sequence. Deletions remove nucleotides, and insertions add nucleotides. Consider the following sequence of bases in RNA:. Answer: nucleotides.
Output: A frameshift mutation is a deletion or insertion of one or more of what that changes the reading frame of the base sequence?
The science passage defines frame mutation and the main compoment here is nucleotides. Hence the generated question is apt.

New input case for you: Passage: Reflected waves have the same speed and frequency as the original waves before they were reflected. However, the direction of the reflected waves is different. When waves strike an obstacle head on, the reflected waves bounce straight back in the direction they came from. When waves strike an obstacle at any other angle, they bounce back at the same angle but in a different direction. This is illustrated in the Figure below . In this diagram, waves strike a wall at an angle, called the angle of incidence. The waves are reflected at the same angle, called the angle of reflection, but in a different direction. Notice that both angles are measured relative to a line that is perpendicular to the wall. Answer: angle of reflection
Output:
When waves are reflected at the same angle, what is it called?