当たる: a ball hitting a window and people meeting conditions
Use the window and conditions before に to distinguish physical contact from applicability, preserving the impact and the request to apply.
A contact target and an applicable condition
当たる (あたる) means hit or apply. 窓に names the window struck by the ball; 条件に names the conditions that people meet.
Read the object before に. A physical contact target and a condition of applicability have different relations to the same verb.
Reported contact and a request to apply
「投げたボールが窓に当たって大きな音がした。」 (The thrown ball hit the window with a loud bang.) The thrown ball actually hit the window with a loud bang. The sentence reports contact and sound, without adding damage to the window or an injury.
「次の条件に当たる人は受付で申請してください。」 (People who meet the following conditions should apply at reception.) People meeting the following conditions are asked to apply at reception. 条件に当たる expresses applicability; the request does not report a completed or approved application.
Identify the relation linked by に
The ball is linked to 窓に当たる as its contact target. The people are linked to 条件に当たる as the conditions they meet. Those stated objects distinguish impact from applicability.
Keep the reported impact and sound separate from the application request. Neither a damage result nor a completed application follows merely from the relation expressed by 当たる.
How do the ball hitting a window and people meeting conditions differ in the 当たる examples?
Show the answer and why
The ball makes physical contact with the window. The people meet conditions and are asked to apply. No window damage or completed or approved application is reported.