O Level Physics: Uses of an Oscilloscope — Practice Questions (Cambridge 5054)

These are original questions written for Marlbridge, for revision and practice on this content. They are not reproduced past-paper questions, and they do not replicate the exam’s exact structure, question count or mark tariffs — Cambridge International holds copyright in its own papers. Use these alongside the official past papers available from your board.

Related: Electricity and magnetism study guide and Electricity and magnetism revision notes

Uses of an oscilloscope is syllabus section 4.6 of Cambridge O Level Physics (5054), syllabus for 2026, 2027 and 2028. An oscilloscope displays how a potential difference changes with time. You must describe its use to display waveforms and describe how to measure p.d. with the Y-gain and short intervals of time with the timebase. The structure of an oscilloscope is not required. These questions cover both learning outcomes and link them to a.c. supplies (4.5) and sound waves (3.4). For circuit and electromagnetism questions, use the Electricity and magnetism practice questions.

How do you read an oscilloscope trace?

Control	Units	What it tells you
Y-gain (vertical sensitivity)	volts per division (V/div)	p.d. = number of vertical divisions x Y-gain
Timebase (horizontal)	time per division (s/div, ms/div)	time = number of horizontal divisions x timebase

For a repeating wave, the period T is the time for one complete cycle, and the frequency is f = 1 / T. The peak p.d. is measured from the centre line to the top of the wave; the peak-to-peak p.d. is from the bottom to the top.

Questions

1. State what an oscilloscope displays on its screen. [1]

2. State the purpose of (a) the Y-gain control and (b) the timebase control. [2]

3. An a.c. supply is connected to an oscilloscope. The Y-gain is 2 V/div and the timebase is 5 ms/div. The trace rises 3.5 divisions above the centre line and falls 3.5 divisions below it. One complete wave occupies 4.0 horizontal divisions.

(a) Calculate the peak p.d. of the supply. [2] (b) Calculate the peak-to-peak p.d. [1] (c) Calculate the period of the supply. [2] (d) Calculate the frequency of the supply. [2]

4. A 12 V battery is connected to the oscilloscope with the timebase switched on and the Y-gain set to 5 V/div.

(a) Describe the trace seen. [2] (b) Calculate how many divisions the trace moves from the centre line. [1]

5. A microphone connected to an oscilloscope picks up a note from a tuning fork. The timebase is set to 0.2 ms/div, and one complete wave covers 2.5 divisions.

(a) Calculate the frequency of the note. [3] (b) The tuning fork is struck harder. State and explain how the trace changes. [2] (c) A tuning fork of higher frequency is used. State how the trace changes. [1]

6. A trace shows only part of one wave, because the waves are too spread out. State which control should be adjusted and in which direction, so that several complete waves are seen. [2]

7. A trace is so tall that its peaks are off the top of the screen. State which control should be adjusted and how. [2]

8. Explain why it is more accurate to measure the time for several complete waves on the screen, rather than for one. [2]

9. An oscilloscope is used to measure a short time interval. A loudspeaker sends a sound pulse towards a wall, and a microphone next to the loudspeaker detects both the outgoing pulse and its echo. On the screen, the two pulses are 6.0 divisions apart. The timebase is 0.5 ms/div and the speed of sound in air is 340 m/s.

(a) Calculate the time between the two pulses. [2] (b) Calculate the distance from the microphone to the wall. [3]

10. A student describes how to measure the peak p.d. of an a.c. supply with an oscilloscope. Write a method in steps. [4]

Answers

1. A graph of p.d. (voltage) against time / a waveform [1].

2. (a) Sets how many volts each vertical division represents (vertical scale), so p.d. can be measured [1]. (b) Sets the time represented by each horizontal division (horizontal scale), so time intervals can be measured [1].

3. (a) Peak p.d. = 3.5 div x 2 V/div [1] = 7.0 V [1]. (b) 7.0 div x 2 V/div = 14 V [1]. (c) T = 4.0 div x 5 ms/div [1] = 20 ms (0.020 s) [1]. (d) f = 1 / T = 1 / 0.020 [1] = 50 Hz [1].

4. (a) A straight horizontal line [1], moved up (or down) from the centre line because the p.d. is steady (d.c.) [1]. (b) 12 V / 5 V/div = 2.4 divisions [1].

5. (a) T = 2.5 div x 0.2 ms/div = 0.5 ms [1] = 5.0 x 10^-4 s; f = 1 / T [1] = 2000 Hz [1]. (b) The wave becomes taller (greater amplitude) [1], because a louder sound has a larger amplitude, but the spacing (period) stays the same [1]. (c) The waves are closer together (more waves across the screen / shorter period) [1].

6. The timebase [1]; increase the time per division (slower sweep), so more cycles fit on the screen [1].

7. The Y-gain [1]; increase the volts per division (reduce the sensitivity), so the trace is smaller [1].

8. Reading several waves reduces the effect of the uncertainty in judging where a wave starts and ends [1]; the total time is divided by the number of waves to give a more accurate period [1].

9. (a) Time = 6.0 div x 0.5 ms/div [1] = 3.0 ms (3.0 x 10^-3 s) [1]. (b) Total distance travelled = speed x time = 340 x 3.0 x 10^-3 = 1.02 m [1]; the sound travels to the wall and back, so divide by 2 [1]; distance = 0.51 m [1].

10. Any four [1 each]: connect the supply to the Y-input; switch on the timebase so a wave is displayed; adjust the Y-gain so the whole wave fits on the screen and is as tall as possible; centre the trace on the middle line; count the vertical divisions from the centre line to a peak; multiply by the Y-gain setting to find the peak p.d.

Where marks are usually lost

• Using peak-to-peak divisions when the question asks for the peak p.d.
• Forgetting to convert ms to s before calculating f = 1 / T.
• Forgetting to halve the echo time or distance.
• Mixing up the Y-gain (volts) and timebase (time) controls.
• Describing the structure of the oscilloscope, which the syllabus says is not required.

Frequently asked questions

Do I need to know how an oscilloscope works inside? No. The 5054 syllabus says the structure of an oscilloscope is not required. You need to use the Y-gain and timebase to make measurements.

How do I find frequency from a trace? Count the divisions for one complete wave, multiply by the timebase setting to get the period in seconds, and use f = 1 / T.

What does a d.c. supply look like on an oscilloscope? With the timebase on, a horizontal line displaced above or below the centre line by an amount that shows the p.d.

Official syllabus

Cambridge O Level Physics (5054) syllabus for examination in 2026, 2027 and 2028, Topic 4 Electricity and magnetism, section 4.6 Uses of an oscilloscope, published by Cambridge International Education.