CIE AS Physics (9702) exams from 2022

Revision Notes

7.1.2 Cathode-Ray Oscilloscope

Cathode-Ray Oscilloscope

  • A Cathode-Ray Oscilloscope is a laboratory instrument used to display, measure and analyse waveforms of electrical circuits
  • An A.C. current on an oscilloscope is represented as a transverse wave. Therefore you can determine its frequency and amplitude
  • The x-axis is the time and the y-axis is the voltage (or y-gain)


CRO diagram, downloadable AS & A Level Physics revision notes

Diagram of Cathode-Ray Oscilloscope display showing wavelength and time-base setting


  • The period of the wave can be determined from the time-base This is how many seconds each division represents measured commonly in s div-1 or s cm-1
  • Use as many wavelengths shown on the screen as possible to reduce uncertainties
  • Dividing the total time by the number of wavelengths will give the time period T (Time taken for one complete oscillation)
  • The frequency is then determined through 1/T


Worked example

Worked example - CRO (1), downloadable AS & A Level Physics revision notes

Worked example - CRO (2), downloadable AS & A Level Physics revision notes

Exam Tip

The time-base setting varies with units for seconds (commonly ms) and the unit length (commonly mm). Unit conversions are very important for the calculate of the time period and frequency

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