RC filter on the scope

// A generator into an RC low pass, both ends on the scope.
//
// R = 1.6 k, C = 100 nF. The corner is where the capacitor's reactance equals
// the resistance:
//
//   f0 = 1 / (2 pi R C) = 1 / (2 pi x 1600 x 100e-9) = 995 Hz
//
// The generator is set to 1 kHz, which is as good as on the corner, so the
// filtered trace (blue, CH2) should come out at
//
//   |H| = 1 / sqrt(1 + (2 pi f R C)^2) = 0.705
//
// of the yellow one, and a whole eighth of a cycle behind it. 2 V in, 1.41 V
// out. Count the divisions: 2 V/div vertically, 400 us/div across.
//
// Things to try. Take the frequency to 100 Hz and the two traces sit on top of
// each other; take it to 10 kHz and the blue one nearly vanishes, down by a
// factor of ten. Swap the generator to a square wave and watch the RC round
// the corners off, which is the same filter doing the same thing to every
// harmonic at once. Make C ten times bigger and the corner moves down a
// decade.