Final answer:
Increasing the pulse repetition period while keeping other factors unchanged will result in a decrease in the duty factor, as the active time remains the same while the period of the cycle is extended.
Step-by-step explanation:
When all other factors remain unchanged, and the pulse repetition period increases, the duty factor decreases. The duty factor, also known as duty cycle, is the percentage of time that a system is in an "active" state as compared to the total time it takes to complete one cycle. Since the duty factor is a ratio of the pulse duration to the pulse repetition period, increasing the pulse repetition period without changing the pulse duration will result in a lower duty factor. This is because the pulse is active for the same amount of time, but the overall period has grown, thereby reducing the proportion of time that the pulse is active (duty factor).