Time-base setting from wave period and display width

Steps:

• Frequency is 5 kHz, so period T = 1/f = 1/5000 s = 200 μs.
• Display shows one full wave (period) spanning 2 cm horizontally.
• Time-base = T / width in cm = 200 μs / 2 cm = 100 μs cm⁻¹.
• This setting displays the 5 kHz wave appropriately across the screen.

Why B is correct:

• 100 μs cm⁻¹ matches the period of 200 μs over 2 cm, per the CRO time-base definition (time per unit length on horizontal axis).

Why the others are wrong:

• A: 10 μs cm⁻¹ is too fast, showing 20 periods in 2 cm (overly compressed display).
• C: 10 ms cm⁻¹ is too slow, showing only 0.02 periods in 2 cm (wave barely visible).
• D: 100 ms cm⁻¹ is even slower, showing 0.002 periods in 2 cm (no visible wave).

Final answer: B