Digital and analog signals

Answer Key - Grade 8 Science Worksheet - Building Confidence

Circle the best answer, or write your answer on the line.

1. 1.

   Ari's sensor stores each brightness reading as 3 bits (each bit is a 0 or a 1). How many different brightness levels can it store?

   8 levels
2. 2.

   Bo's game stores each color shade as 4 bits (each bit is a 0 or a 1). How many different shades can 4 bits tell apart?

   16 levels

3. Read this first

   Use this

   (example data). Top: an analog signal, a smooth wave. Bottom: a digital signal of 8 pulses, read as 1, 0, 1, 1, 0, 0, 1, 0.

4. 3.

   Using the signal pair, which signal is digital, and why, Jun?

   • The top one, since it is made of separate 0s and 1s
   • The bottom one, since it has two levels, 1 and 0
   • Both are digital, since both signals carry a message
   • The top one, since it is smooth and so is copied exactly
5. 4.

   A thermometer's liquid column can stop at any height. Is that signal analog or digital, and why, Kira?

   • Digital, since a liquid column is either up or down
   • Analog, since a thermometer is made of liquid
   • Analog, since any height in its range is possible
   • Digital, since temperatures are written as numbers
6. 5.

   A text message is stored as groups of 0s and 1s. Is that signal analog or digital, and why, Luz?

   • Neither, since a message is not a signal
   • Analog, since it travels through the air
   • Digital, since each pulse is a 0 or a 1
   • Analog, since letters change smoothly

7. Copies of a recording (example data)

   copy	tape difference (%)	digital file difference (%)
   1	2	0
   2	4	0
   3	7	0
   4	11	0
   5	16	0

8. 6.

   Using the table, what happens to the tape copies' difference from the original as more copies are made, Milo?

   • It stays the same, since a copy is a copy
   • It grows at first, then stops
   • It shrinks, since later copies are cleaner
   • It gets bigger with every copy
9. 7.

   What does the digital file's column show, Noah?

   • It matched the original in all five copies
   • It got better with every copy
   • It got worse, but more slowly than the tape
   • It could not be copied
10. 8.

    Which statement does the whole table support, Pia?

    • Tape copies stay as close to the original as the first copy
    • Both kinds got worse, at different speeds
    • Tape drifted further with each copy; digital did not
    • Digital copies are better because 0 is a small number
11. 9.

    Which bits does the receiver read from these four pulses, Ren?

    • 1, 1, 1, 1
    • 0.8, 0.2, 0.9, 0.1
    • 1, 0, 1, 0
    • 0, 1, 0, 1
12. 10.

    The sender sent 1, 0, 1, 1, 0. Did noise change any bit the receiver reads, Zee?

    • Yes, because the heights are not exactly 0 and 1 anywhere
    • Yes, because the 0.8 should have been a full 1.0 pulse
    • No, every pulse is on the correct side of 0.5
    • Yes, the 1.2 is higher than a full pulse