Acceleration is defined as the change in velocity divided by

Time elapsed

Explanation:

Acceleration is a vector quantity. It is defined as:

where

v is the final velocity

u is the initial velocity

t is the time elapsed

Acceleration is measured in meters per second squared (m/s^2). It must be noticed that acceleration is a vector, so it also has a direction. In particular:

- when acceleration is negative, it means that the object is slowing down, so acceleration is in opposite direction to the velocity

- when acceleration is positive, it means that the object is speeding up, so acceleration is in the same direction as the velocity

wavelength variability is the right one