Given a pulse with 4 cycles at 2 MHz, what is the pulse duration?

Given a pulse with 4 cycles at 2 MHz, what is the pulse duration?

• A. 2 μs
• B. 0.5 μs
• C. 8 μs
• D. 1 μs

Answer: (A)

The duration of a pulse is the number of cycles it contains times the period of one cycle. The period is the reciprocal of frequency: T = 1/f. With a frequency of 2 MHz, one cycle lasts 1 / 2,000,000 seconds = 0.5 microseconds. Four cycles therefore span 4 × 0.5 μs = 2 μs. So the pulse duration is 2 μs. (For context: 0.5 μs would be just one cycle at this frequency; 8 μs would correspond to 16 cycles; 1 μs would be two cycles.)

The duration of a pulse is the number of cycles it contains times the period of one cycle. The period is the reciprocal of frequency: T = 1/f. With a frequency of 2 MHz, one cycle lasts 1 / 2,000,000 seconds = 0.5 microseconds. Four cycles therefore span 4 × 0.5 μs = 2 μs. So the pulse duration is 2 μs.

(For context: 0.5 μs would be just one cycle at this frequency; 8 μs would correspond to 16 cycles; 1 μs would be two cycles.)