question shifted to Input across RC circuit is not showing a square wave though the input is a square wave as it was unclear
Electronic – RC circuit charging and discharging by square wave not giving a square wave across input on oscilloscope
function generatorlow passoscilloscopetime constanttransient
Related Solutions
The author of the lab wants you to see the typical step response on which you can measure the time constant.
If you put in a sine wave, you will get out a sine wave with a different amplitude and phase. Try doing just that and then sweeping the frequency on the function generator.
The right hand op-amp looks like a comparator (with an open collector output). The emitter I suspect is pin 1 and this is tied to -15 V. Open collector outputs require a pull-up resistor hence the need for R5 in your circuit.
If you could link where you found this circuit this could be confirmed. I think the comparator matches the pin out of the LM311: -
Collector = pin 7 and emitter = pin 1.
Best Answer
With the fast edge only being 50% of the input waveform (shown on scope), your generator output resistance is the same value as the R in the RC lowpass. You have an instantaneous voltage divider for the fast edge.
simulate this circuit – Schematic created using CircuitLab