Given scientific fact as input, generate the question from this fact such that it can be answered from the input.

Example Input: Light retains its original color under water because frequency remains the same when light is refracted.
Example Output: Light retains its original color under water because what remains the same when light is refracted?

Example Input: Together, the muscular and skeletal organs are known as the musculoskeletal system.
Example Output: Together, the muscular and skeletal organs are known as what?

Example Input: In an electromagnetic wave, the crests and troughs represent oscillating fields.
Example Output:
In an electromagnetic wave, what do the crests and troughs represent?