Directly Related

When one goes up, the other also goes up.

When one goes down, the other also goes down.

They always move in the same direction.

You are ordering coffees. Turn the knob to order more.

1
Turn the knob
1
Coffees
$5
Total cost

More coffees ordered means more money spent. Both values move in the same direction. That is what directly related means.

Turn the knob and watch both values climb together on the graph.

1

When two things are directly related, the graph slopes up from left to right. Both axes climb together.

In ultrasound, intensity and amplitude are directly related. Turn up the power and both increase together.

Low
Turn the power knob
Low
Amplitude
Low
Intensity

These terms will come up in detail later. For now, notice: they move in the same direction. Directly related.

Intensity
Definition: How strong or powerful the sound wave is.

Think of it like volume on a speaker. Higher intensity means a louder, stronger signal.
Amplitude
Definition: How tall the wave is from its resting position to its peak.

When intensity goes up, amplitude goes up. When intensity goes down, amplitude goes down. They are directly related.

Quick Check

If one value increases and the other also increases, they are:
Intensity is directly related to amplitude. If intensity increases, what happens to amplitude?
On a graph, a direct relationship slopes: