A periodic wave is a wave that follows a repeating pattern as it propagates through space. That is, the oscillating pattern repeats at regular intervals of time. This repeating motion is also known as periodic motion

Explanation:

What is simple harmonic motion?

"Simple harmonic motion is a type of motion directed along a straight line, whose acceleration is fixed towards a point  and is proportional to its distance from that point"

An object is said to be in simple harmonic motion if the following occurs:

• It moves in a uniform path.

• A variable force acts on it.

• The magnitude of the force is proportional to the displacement of the mass.

• The force is always opposite in direction to the displacement direction.

• The motion is repetitive and a round trip, back and

  forth, is always made in equal time periods

r = ρ x length / area  

ρ = r x area / length  

ρ is in ohm-meters  

in basic units, it is m³kg/s³a²  

i think this is it.