CAIE A-Level Physics 7.1.3 Using an Oscilloscope

Practise using CRO time-base and y-gain settings to find period, frequency and amplitude, interpreting divisions, peak readings and units.

Exam points

use the CRO time-base to determine period and frequency
use the CRO y-gain to determine amplitude and account for divisions and units
interpret a CRO trace consistently, including peak or peak-to-peak readings

[Maximum number: 2]

The waveform of a sound wave is displayed on the screen of a cathode-ray oscilloscope (c.r.o.), as shown in Fig. 5.1.

Fig. 5.1

The time-base setting is $0.20 \mathrm{~ms} \mathrm{~cm}^{-1}$ .
Determine the frequency of the sound wave.

$T=4.0 \times 0.20=0.80(\mathrm{~ms})$ or $8.0 \times 10^{-4}(\mathrm{~s})$

C1

$\begin{aligned} f =1 / 8.0 \times 10^{-4} =1300 \mathrm{~Hz} \end{aligned}$

A1

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7.1.3—The use of the time-base and y-gain of a cathode-ray oscilloscope (CRO) to question 1