A microphone linked to the Y-plates of a cathode-ray oscilloscope (c.r.o.) is positioned in front of a loudspeaker. The c.r.o. screen shows the trace. The time-base setting is $0.5\,\text{ms cm}^{-1}$ and the Y-plate sensitivity is $0.2\,\text{mV cm}^{-1}$. What is the frequency of the sound produced by the loudspeaker and what is the amplitude of the trace on the c.r.o.?
- 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 $1.2\,\text{mV}$