plumiDigitising signals: OCR A‑Level Physics B questions
OCR A-Level Physics B past-paper questions on 3.1.1.3 Digitising signals, 2016–2025, with mark schemes and examiner’s reports where available.
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Q26(a)
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All 57 questions on Digitising signals, as a list
- June 2025, Paper 1, Q9 (1 mark): A car registration plate recognition camera is required to recognize 1 185 856 000 alternative values. How many bits are needed to store 1 185 856 000 alternati
- June 2025, Paper 2, Q7 (3 marks): A scan of a phonoautogram (lines 18–28) produces a signal variation of 2 mV and a noise level of 75 μV. Calculate the number of bits to best represent this samp
- June 2025, AS Paper 1, Q4 (1 mark): An analogue signal has amplitude 80 mV and picks up noise of amplitude 5 mV. The number of useful quantisation levels needed to digitise this signal is equal to
- June 2025, AS Paper 1, Q26(a) (1 mark): Suggest one advantage of having a digital, rather than analogue, output from the sensor. [1]
- June 2025, AS Paper 1, Q26(b)(ii) (2 marks): Calculate the number of bits required to encode 1024 levels. Number of bits required = bits [2]
- June 2025, AS Paper 1, Q26(c) (2 marks): The highest vibration frequency of interest is 2 kHz. Calculate the minimum number of samples that must be recorded per second. Number of samples = s–1 [2]
- June 2025, AS Paper 1, Q26(d) (2 marks): A different sensor generates 15 bits per sample and 8000 samples per second. The output data is transmitted to a computer system using a wireless network. An ad
- June 2024, Paper 1, Q32(a) (2 marks): Fig. 32.1 shows the signal given to the students. Fig. 32.1 6 5 4 signal 3 level / mV 2 1 0 0 1 2 3 4 5 6 time / ms The students: • sample the signal every mill
- June 2024, Paper 1, Q32(b) (2 marks): Fig. 32.3 shows another signal given to the student. Fig. 32.3 6 5 4 signal 3 level / mV 2 1 0 0 1 2 3 4 5 6 time / ms Explain why, when this signal is digitise
- June 2024, AS Paper 1, Q22(a)(i) (1 mark): the number of levels Number of levels = [1]
- June 2024, AS Paper 1, Q22(a)(ii) (1 mark): the number of bits required to encode the signal Number of bits = [1]
- June 2024, AS Paper 1, Q22(a)(iii) (1 mark): the time between samples. Time = μs [1]
- June 2024, AS Paper 1, Q22(b) (2 marks): The quality of the digital signal will be acceptable if the minimum sampling rule is met: minimum rate of sampling > 2 × maximum frequency of signal Show whethe
- June 2023, Paper 1, Q11 (1 mark): A signal is recorded. The total amplitude of the signal voltage varies from zero to 2.56 mV. The noise in the signal is 2.5 × 10–3 mV. The highest frequency com
- June 2023, Paper 1, Q32(a)(ii) (1 mark): The number of bits per image is reduced by a process called compression. The camera captures 30 images each second. A recording of a 40-minute lesson is uploade
- June 2023, AS Paper 1, Q25(c) (2 marks): How many bits per pixel are required to resolve over 16 million different colours? bits per pixel = [2] The dashcam records 22 frames of video per second and co
- June 2023, AS Paper 2, Q7(b)(i) (3 marks): Explain how the eight voltage levels illustrated can be encoded with a three-bit binary number and give the binary code which would represent a value of 3 mV. b
- June 2023, AS Paper 2, Q7(b)(ii) (2 marks): Explain why the audio signal produced from this code will sound different from the original clarinet note. [2]
- June 2023, AS Paper 2, Q7(c) (2 marks): A piece of music for solo clarinet lasts for 1 minute and 39 seconds. Assuming that it is digitised with eight voltage levels (3-bit coding) sampled every 0.25
- June 2023, AS Paper 2, Q7(d) (2 marks): A commercial download of the music described in (c) is a stereophonic (two-channel) recording sampled at 44.1 kHz with 8-bit coding. Calculate the time taken to
- June 2022, Paper 1, Q4 (1 mark): The variation of a signal without noise is 140 mV. The maximum number of useful bits to sample the same signal with noise is 3. What is the noise variation in t
- June 2022, Paper 1, Q7 (1 mark): A sound signal with a highest frequency component of 8 kHz is digitised. The signal to noise ratio of the recording is 103. Which row in the table below gives t
- June 2022, AS Paper 1, Q18 (1 mark): A signal is received with a signal-to-noise ratio of 7.5. Which is the best choice of the number of bits used to sample this signal? A 2 B 3 C 7 D 8 Your answer
- June 2022, AS Paper 1, Q25(a) (1 mark): Determine the number of different shades of grey that can be represented by 8 bits. number of shades = [1]
- June 2022, AS Paper 1, Q25(b) (2 marks): Calculate the time taken to transmit this image at a rate of 54 megabits per second. time taken = s [2]
- June 2022, AS Paper 2, Q2(b) (1 mark): A more complex sound signal is a sum of musical notes with a frequency range 18 Hz to 24 kHz. It is to be encoded as a digital signal before transmission. Calcu
- June 2022, AS Paper 2, Q6(b)(iv) (6 marks): This question is about using remote sensors to make measurements on the planet Mars. (iv)* As much of the data recorded by Perseverance on its 8 Gb memory unit
- November 2021, Paper 1, Q32(a) (1 mark): Explain why the sampling frequency should be at least 25 kHz. [1]
- November 2021, Paper 1, Q32(b) (2 marks): Suggest and explain the number of bits per sample you would use to digitise this waveform. [2]
- November 2021, AS Paper 1, Q2 (1 mark): Each pixel in an image is one of 65 000 different colours. How many bits are required to store the colour information for each pixel? A 5 B 12 C 15 D 16 Your an
- November 2021, AS Paper 1, Q6 (1 mark): Which of these is a benefit of digital signals over analogue signals? A Amplifying a digital signal boosts the signal and noise. B Digital signals never need to
- November 2020, Paper 1, Q3 (1 mark): Quantisation errors can best be reduced by A decreasing the bits per sample. B decreasing the sampling frequency. C increasing the sampling frequency. D increas
- November 2020, Paper 1, Q4 (1 mark): The bit rate (bits s−1) of the digitised sample is: 4 A 3 B 30 C 1110 D 3000 Your answer [1] 4 The following information is for use in questions 5 and 6. A B C
- November 2020, Paper 1, Q36(a)(i) (1 mark): Show that the information rate needed for this digitisation during playback is greater than 1 Mbit s−1. [1]
- November 2020, Paper 1, Q36(a)(ii) (2 marks): A CD typically stores 840 MBytes. Show that the total playback time is about 80 minutes for such a CD. time = minutes [2]
- November 2020, Paper 1, Q36(b)(i) (1 mark): State the evidence from Fig. 36.1 that there is more than one frequency present in the waveform. [1] 26 A sound spectrum displays the different frequencies pres
- November 2020, Paper 1, Q36(b)(ii) (1 mark): Suggest why it is possible to ignore signals of under about 5 mV. [1]
- November 2020, Paper 1, Q36(b)(iii) (1 mark): Some humans have perfect pitch judgement for sound, accurate to ± 1 Hz. Calculate the minimum number of bits needed to code for this precision for the frequency
- November 2020, Paper 1, Q36(b)(iv) (2 marks): To digitise this 10 ms sample of the sound wave each of the four peaks in the sound spectrum of Fig. 36.2 can be coded by 24 bits. Show that the minimum rate of
- November 2020, Paper 2, Q7(b) (3 marks): State the minimum sampling frequency required to accurately digitise the waveform. Explain your answer. minimum sampling frequency = Hz Explanation: [3]
- November 2020, AS Paper 1, Q5 (1 mark): The diagram shows an analogue signal. V t Which diagram best represents the signal sampled using 3 bits? A B V V t t C D V V t t Your answer [1]
- November 2020, AS Paper 2, Q3(a) (3 marks): Explain why using 9-bit quantisation to sample the signal is not better than using 8-bit quantisation. Justify your answer with an appropriate calculation. [3]
- November 2020, AS Paper 2, Q3(b) (2 marks): The signal consists of two stereo channels, each sampled with 8-bit quantisation as stated in part (a). The sampling rate is 44.1 kHz. Calculate the rate of tra
- June 2019, Paper 1, Q8 (1 mark): A signal is digitised by sampling at 22 kHz. The total voltage variation is 2.0 V and the noise voltage variation is 1.0 mV. Which statement is correct? A The h
- June 2018, Paper 1, Q3 (1 mark): How many bits are required to code for 1300 different levels? A 3 B 4 C 10 D 11 Your answer [1]
- June 2018, Paper 1, Q32(a) (2 marks): Show that the time taken for the file to download is greater than 6 minutes. [2]
- June 2018, Paper 1, Q32(b) (2 marks): The video file contains a soundtrack sampled at 16.0 kHz. State and explain the highest frequency of sound that can be recorded on the soundtrack. highest frequ
- June 2018, AS Paper 1, Q24(a) (1 mark): State the minimum rate of sampling that should be used. minimum sampling rate = Hz [1]
- June 2018, AS Paper 1, Q24(b) (2 marks): In this system the = 3000. noise variation Calculate the number of bits that should be used per sample for this system. number = bits [2]
- June 2018, AS Paper 1, Q27(a)(ii) (1 mark): The 5.8 Mbits was downloaded to an Earth receiver at a rate of 110 kbit s−1. Calculate the time taken to download this data. time taken = s [1]
- June 2017, Paper 1, Q4 (1 mark): A signal is being digitised by sampling at 12 kHz. The total voltage is 5.0 V and the noise voltage is 4.9 mV. Which statement is correct? V total 3 A 10 . V no
- June 2017, AS Paper 1, Q5 (1 mark): A spacecraft sends images of Pluto to Earth. Each image consists of 1024 × 1024 pixels. Each pixel is coded by 12 bits. The data transfers at a rate of 200 byte
- June 2017, AS Paper 1, Q27(a) (3 marks): Explain how this signal can be digitised. You may draw on Fig. 27.1 to support your answer. �������������������������������������������������������������������
- June 2017, AS Paper 1, Q27(b)(iii) (2 marks): Use the data to estimate the number of bits stored in the file per second of sound recorded. bits per second = [2]
- June 2017, AS Paper 2, Q7(d) (3 marks): The data for the image in Fig. 7.1 was sent from the Mariner space probe back to Earth at a rate of 117.6 kilobits s−1. The complete image was transmitted in 22
- June 2016, AS Paper 1, Q23(a) (2 marks): Determine the number of bits per sample that have been used to digitise the signal. Explain your reasoning. number of bits per sample = [2]
- June 2016, AS Paper 1, Q23(b) (1 mark): Estimate the frequency of the analogue signal shown in Fig. 23. Make your method clear. frequency = Hz [1]
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