Period of a 25 Hz signal?

• A. 0.04 s
• B. 0.25 s
• C. 4 s
• D. 0.4 s

Answer: (A)

Frequency is how many cycles occur each second, and the period is the time for one cycle. The period T is the reciprocal of the frequency f, so T = 1/f. For 25 Hz, T = 1/25 seconds, which equals 0.04 s. So each cycle lasts 0.04 seconds. The other numbers would correspond to different frequencies (for example, 0.25 s is a cycle time for 4 Hz, 4 s for 0.25 Hz, and 0.4 s for 2.5 Hz), not for 25 Hz.