Frequency from CRO Time Base and Horizontal Distance

Steps:

• CRO horizontal axis shows time, calibrated by time base setting (e.g., ms/div).
• Measure horizontal distance between wave peaks to get period in divisions.
• Multiply distance by time base to find actual period T in seconds.
• Calculate frequency f = 1/T.

Why B is correct:

• Frequency is inversely proportional to period (f = 1/T), directly from time-based horizontal measurement and time base control.

Why the others are wrong:

• A: Amplitude requires vertical distance measurement on screen.
• C: Speed needs wavelength or propagation distance, not available from time-only data.
• D: Wavelength is spatial, not measurable from CRO's time-domain display.

Final answer: B