Which device is typically used to visualize waveforms, showing crests and troughs?

An oscilloscope is an instrument specifically designed to visualize waveforms by displaying their variation over time. When using an oscilloscope, you can see the graphical representation of the voltage or current waves, where the peaks correspond to the crests and the valleys correspond to the troughs of the waveforms. This allows for the analysis of various wave properties such as amplitude, frequency, and waveform shape, which are crucial for understanding electrical signals and other oscillatory phenomena.

In contrast, an electroscope is a device used to detect electric charge, and while it provides information about static electricity, it does not visualize waveforms. Conductors are materials that allow the flow of electric current, while insulators resist current flow; neither of these terms pertains to the visualization of waveforms. Thus, the oscilloscope is uniquely suited for this purpose, making it the correct choice for visualizing the crests and troughs of waves.