Definition check: Band-pass filter passband and stopband Does a band-pass filter reject all frequencies between its lower and upper critical frequencies and pass all others, or is it the reverse?

Introduction / Context:
Identifying whether a filter passes or rejects a frequency band is fundamental when designing communications channels, audio crossovers, or sensor front-ends. The statement given swaps the meaning of band-pass and band-stop.

Given Data / Assumptions:

• Lower critical frequency fL, upper critical frequency fH define the 3 dB points in many specifications.
• Band-pass filters intentionally pass frequencies between fL and fH.
• Outside this band, attenuation increases (stopbands).

Concept / Approach:

By definition, band-pass filters have a central passband and two stopbands (below fL and above fH). The magnitude response is highest within the band and rolls off outside it, often with slopes defined by filter order and type (Butterworth, Chebyshev, etc.).

Step-by-Step Solution:

Verification / Alternative check:

Examine a series RLC between source and load: around resonance f0, the impedance is low and the circuit passes the band near f0 (between fL and fH), attenuating frequencies far below or above—classic band-pass behavior.

Why Other Options Are Wrong:

• “True” variants contradict the fundamental definition; Q or filter type does not change definitions.
• The “geometric mean only” statement confuses the center frequency with the width of the passband.

Common Pitfalls:

Assuming that because both band-pass and band-stop have two critical frequencies, their functional descriptions are interchangeable. Always tie the label to what happens inside the band.

Final Answer:

False