Period is the reciprocal of frequency

Steps:

• Convert 5 GHz to Hz: 5 × 10^9 Hz.
• Use formula T = 1/f, where T is period in seconds.
• Compute T = 1 / (5 × 10^9) = 2 × 10^{-10} s.
• Convert to picoseconds: 2 × 10^{-10} s = 200 ps (1 ps = 10^{-12} s).

Why A is correct:

• By definition, period T = 1/f, so for f = 5 × 10^9 Hz, T = 200 ps exactly.

Why the others are wrong:

• B: 2 ns equals 2000 ps, which is T for 0.5 GHz (10× lower frequency).
• C: 20 ns equals 20,000 ps, which is T for 50 MHz (100× lower frequency).
• D: 200 μs equals 2 × 10^5 μs, which is T for 5 kHz (10^6× lower frequency).

Final answer: A