Compare Digital and Analog Signals - Physics

1. What is meant by attenuation in signal transmission?

   A reduction in signal amplitude as it propagates. Signal weakens due to resistance and energy loss in the medium.

2. What is quantization in analog-to-digital conversion?

   Rounding amplitudes to the nearest discrete level. Converts continuous amplitudes to nearest allowed discrete value.

3. What is the main disadvantage of analog transmission regarding noise?

   Noise adds directly to the signal and accumulates with distance. Cannot separate noise from signal; both amplify together.

4. Identify the correct statement about error detection and correction in transmission: analog or digital?

   Digital systems can use error detection and correction codes. Extra bits can detect and fix transmission errors mathematically.

5. What is the Nyquist sampling condition for a maximum signal frequency $f_{max}$?

   Sample at $f_s \ge 2f_{max}$. Must sample at least twice the highest frequency to avoid aliasing.

6. Identify the term for distortion caused by sampling below $2f_{max}$.

   Aliasing. High frequencies appear as false low frequencies when undersampled.

7. What is an analog signal in terms of how its amplitude varies with time?

   A continuous-time signal with continuously varying amplitude. Amplitude can take any value within a range at any instant.

8. Which option best matches the signal type to a microphone output before conversion: analog or digital?

   Analog. Sound waves create continuous voltage variations in microphones.

9. What is a digital signal in terms of the set of amplitude levels it uses?

   A signal that uses discrete amplitude levels (often $0$ and $1$). Only specific amplitude values are allowed, typically binary.

10. Which option best describes how digital information is represented: continuous values or discrete symbols?

    Discrete symbols (bits). Uses binary digits to represent information as $0$s and $1$s.

11. Which option typically requires a digital-to-analog converter (DAC) to drive a speaker?

    A digital signal. Speakers need continuous voltages, not discrete bits.

12. Which option is generally more robust to small amplitude noise in transmission: analog or digital?

    Digital. Small noise won't flip bits if below decision threshold.

13. Which choice best describes how small noise affects digital bits: additive or thresholded?

    Thresholded (small noise often does not change the bit). Noise below threshold doesn't flip bits between levels.

14. Which option is more suitable for error detection and correction: analog or digital?

    Digital. Discrete levels allow parity bits and checksums.

15. Which option is easier to store and copy without degradation: analog recordings or digital data?

    Digital data. Perfect copies possible since only discrete values are stored.

16. What is aliasing in digital sampling of an analog signal?

    High-frequency content appears as a lower frequency due to undersampling. Frequencies above $f_s/2$ fold back into the sampled spectrum.

17. Which choice best describes how noise affects analog amplitude: additive or thresholded?

    Additive (noise directly changes the amplitude). Noise voltage adds to signal voltage, distorting it.

18. What is a digital signal in terms of how its amplitude varies with time?

    A signal with discrete amplitude levels (often binary). Amplitude can only take specific values, typically 0 or 1 for binary.

19. Identify the main trade-off when increasing sampling rate in digital transmission.

    Higher data rate (more bandwidth/storage needed). More samples per second means more data to transmit/store.

20. What is the typical relationship between bit depth and quantization levels for $N$ bits?

    $2^N$ quantization levels. Each bit doubles the number of possible amplitude levels.

21. Which option typically uses repeaters that regenerate clean pulses: analog or digital?

    Digital. Can detect and recreate original discrete levels.

22. What is the main trade-off of digital transmission compared with analog regarding bandwidth needs?

    Digital often requires higher bandwidth for the same information rate. Multiple bits needed to represent each analog sample value.

23. Identify the device that boosts an analog signal amplitude but also boosts noise: amplifier or regenerator?

    Amplifier. Increases all signal components equally, including unwanted noise.

24. What is the main advantage of digital transmission regarding noise accumulation?

    It can be regenerated, so noise does not accumulate as much. Repeaters can restore original discrete levels, removing noise.

25. What does bit depth (number of bits) control in a digital representation of amplitude?

    The number of quantization levels and amplitude resolution. More bits allow finer amplitude distinctions.

26. Which option best describes digital transmission: continuous or discrete values?

    Discrete values. Amplitude is restricted to specific levels like 0 and 1.

27. What is the number of quantization levels for an $n$-bit digital signal?

    $2^n$ levels. Each bit doubles the number of possible amplitude levels.

28. Which option best matches the signal type used internally by a computer CPU: analog or digital?

    Digital. CPUs process binary data using logic gates and transistors.

29. Identify the device that restores a digital pulse train to ideal $0/1$ levels: amplifier or regenerator?

    Regenerator (digital repeater). Detects bit values and outputs clean digital pulses.

30. Which option has a theoretically infinite set of possible amplitude values: analog or digital?

    Analog. Continuous signals have no amplitude restrictions.

31. Which option best describes how analog information is represented: continuous values or discrete symbols?

    Continuous values. Can take any value within a range, like voltage or temperature.

32. Which option has larger quantization error: $N=8$ bits or $N=12$ bits (same input range)?

    $N=8$ bits. Fewer bits means fewer levels, so larger rounding errors.

33. What is sampling in analog-to-digital conversion?

    Measuring the signal amplitude at discrete times. Takes snapshots of the signal at regular time intervals.

34. What is the main disadvantage of analog transmission regarding noise over long distances?

    Noise adds directly to the signal and accumulates with distance. Each amplifier adds more noise, degrading signal quality progressively.

35. What is the main advantage of digital transmission regarding noise accumulation over long distances?

    Repeaters can regenerate bits, limiting cumulative noise effects. Clean bits can be perfectly restored at each repeater station.

36. Which option typically requires an analog-to-digital converter (ADC) to store on a computer?

    An analog signal. Computers process discrete values, not continuous ones.

37. What is quantization in converting an analog signal to digital form?

    Rounding sampled amplitudes to the nearest allowed discrete level. Converts continuous amplitudes to discrete steps, introducing error.

38. What is the Nyquist sampling condition for a maximum frequency $f_{max}$?

    Sampling frequency must satisfy $f_s \ge 2f_{max}$. Prevents aliasing by sampling at least twice the highest frequency.

39. Which option best describes analog transmission: continuous or discrete values?

    Continuous values. Amplitude can smoothly vary between any values.

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