A microphone that is linked to the Y-plates of a cathode-ray oscilloscope (CRO) is positioned in front of a loudspeaker. The CRO screen shows the trace. The time-base setting is $0.5\,\text{s cm}^{-1}$ and the Y-plate sensitivity is $0.2\,\text{mV cm}^{-1}$. Determine the frequency of the sound produced by the loudspeaker and the amplitude of the CRO trace.
- Afrequency $= 330\,\text{Hz}$, amplitude $= 0.6\,\text{mV}$
- Bfrequency $= 330\,\text{Hz}$, amplitude $= 1.2\,\text{mV}$
- Cfrequency $= 670\,\text{Hz}$, amplitude $= 0.6\,\text{mV}$
- Dfrequency $= 670\,\text{Hz}$, amplitude $= 1.2\,\text{mV}$