A shorter pulse has a ____ Q factor.

A shorter pulse has a ____ Q factor.

• A. Higher
• B. Directly
• C. Lower
• D. Inversely

Answer: (C)

Quality factor, or Q, measures how selective a resonator is around its resonant frequency. It’s the ratio of the resonant frequency to the bandwidth over which the system responds (Q = f0 / Δf). A high Q means a sharp, narrow resonance (small Δf); a low Q means a broader resonance (large Δf). A shorter pulse in time carries a wider range of frequencies (the time–frequency trade-off). So exciting a system with a shorter pulse effectively samples a broader bandwidth, which corresponds to a lower Q. In contrast, a longer pulse has a narrower spectrum and would relate to a higher Q.

Quality factor, or Q, measures how selective a resonator is around its resonant frequency. It’s the ratio of the resonant frequency to the bandwidth over which the system responds (Q = f0 / Δf). A high Q means a sharp, narrow resonance (small Δf); a low Q means a broader resonance (large Δf). A shorter pulse in time carries a wider range of frequencies (the time–frequency trade-off). So exciting a system with a shorter pulse effectively samples a broader bandwidth, which corresponds to a lower Q. In contrast, a longer pulse has a narrower spectrum and would relate to a higher Q.