> Hoping to highlight the elusive order in the distribution of the primes, he and his student Ge Zhang had modeled them as a one-dimensional sequence of particles — essentially, little spheres that can scatter light. In computer experiments, they bounced light off long prime sequences, such as the million-or-so primes starting from 10,000,000,019.

It sounds like they simulated shining light on particles that were distributed based on the interval between subsequent primes, then looked for patterns in the resulting diffraction. The title was worded that way for a pun (the chemist revealed interesting information about the pattern by literally shining light on it).

"Shining light" on something is kind of a metaphor for figuratively illuminating something, or showing something more clearly (pretend someone shines light on something in the dark). More precisely, I believe this is saying that a chemist is providing more information about a prime number PATTERN.