Understanding the CRO Measurement

The question asks us to find the frequency of a sine waveform displayed on a Cathode Ray Oscilloscope (CRO).

Calculating Signal Period

We are given the following information:

• The waveform spans 3 complete cycles across 6 horizontal divisions.
• The time base setting is 1 millisecond per division (1 ms/div).

First, let's calculate the total time the 3 cycles occupy on the screen:

Total time span = (Number of horizontal divisions) $\times$ (Time base setting)

Total time span = 6 divisions $\times$ 1 ms/div = 6 ms

This 6 ms represents the time taken for 3 cycles of the waveform. To find the time for one cycle (the Period, T), we divide the total time span by the number of cycles:

Period, $T$ = (Total time span) / (Number of cycles)

$T = 6 \text{ ms} / 3 \text{ cycles} = 2 \text{ ms/cycle}$

Calculating Signal Frequency

The frequency ($f$) of a signal is the reciprocal of its period ($T$). Before calculating, we convert the period from milliseconds to seconds:

$T = 2 \text{ ms} = 2 \times 10^{-3} \text{ s}$

Now, we calculate the frequency using the formula $f = 1/T$:

$f = 1 / (2 \times 10^{-3} \text{ s})$

$f = 1 / 0.002 \text{ Hz}$

$f = 500 \text{ Hz}$

Therefore, the frequency of the signal being measured is 500 Hz.