The graph above shows how the brightness of the sun is related to the time of day.
From the start at the bottom left hand corner until just before 6 am brightness is zero. (It is dark).
Brightness increases as time passes being at maximum about 1 pm when the sun is highest in the sky.
Brightness then falls becoming dark at about 9 pm when the sun sets. Now look at the following graph.
This next graph shows a voltage which slowly rises from zero to a maximum value and then falls suddenly to zero again.
This next graph shows the same thing happening but continues repeating. This is called a WAVEFORM.
The next waveform is called a square waveform because of its shape.
It is at zero for a time and then shoots rapidly to a maximum value and stays there for a time before falling to zero again.
It then repeats itself continuously.
An OSCILLOSCOPE is used to display and measure waveforms.
A common waveform is the SINEWAVE which can alternate between positive and negative voltages.
Note that the horizontal line in all these graphs is called the X axis and the vertical line is the Y axis.
