Effects of phase shift in frequency against period of time:

Instantaneous phase (ϕ) represents an angular shift between two sine waves and is measured in degrees (or radians). 

A sine wave and a cosine wave are 90° (π/2 radians) out of phase with each other.

After a period of time Δt, two sine waves initially synchronized in phase but differing in frequency by Δω degrees (or radians) per second will develop a differential total phase shift (ΔΦ).

Given by the equation: ΔΦ = Δω × Δt.