Answer:
He did not control the event.
The investigation was an observational study.
Step-by-step explanation:
A careful observation of the question given above,
Then context of the question suggests that Newton only observed the action of a prism on white light and on red light meaning he did not influence or control the event. Now, because he did not control the event, his investigation is only term observational study of the action of a prism on white light and on red light.