On a 20 MHz oscilloscope as those used in class, the knob of the time sweep rate shows for the fastest setting the mark of 0.2 microseconds per major division in horizontal direction on the screen. How many full periods of a 5 MHz periodic signal will be observed in one major horizontal division

One.

Explanation:

The period, is defined as the time needed for a given signal to complete a full cycle.As the frequency is defined as the number of full cycles per unit time, we conclude that the period is just the inverse of the frequency.If the frequency of the signal is 5 Mhz, we can calculate the period T as follows:

       

The period of the signal is 0.2 μsec.As the fastest setting for the time sweep rate (which defines what is displayed horizontally) is set at 0.2 μsec per major horizontal division on the screen, we can see exactly 0.2 sec of the signal in each division.As the period is equal to the time for one cycle, and is equal to the time displayed per div (0.2 μsec), we will be able to see one full cycle in one major horizontal division.