Which Frequency Response Graph Correctly Represents a Band Reject Filter?

[smart_worker]

Homework Statement

Homework Equations

The Attempt at a Solution

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Which is the correct frequency response graph for this question? The first graph or the second one?

 

[scottdave]

Band reject implies that it passes everything, except frequencies in the band. Looking at just the positive side: If it is less than pi/3 then it is 1. If it is greater than 2pi/3 then it is also 1. Elsewhere is zero. Well elsewhere is inbetween pi/3 and 2pi/3 (the band to be rejected). Since there is absolute value, you will have a mirror image of the band response across the axis.

Which of the graphs fit this description?

 

[smart_worker]

The second graph fits the description.