I'm having a difficult time understanding the formulas for maximum constructive interference and perfect destructive interference. I know that MCI there's the biggest amplitude? and for PDI it's 0.

The forumlas are

delta phi = 2pi(deltax/lambda)+delta phi
FOR BOTH OF THEM?? I don't get that.

Concentrate on how construcitve and destructive occur. Both are the same, waves same frequency, in phase, or exactly 180 degrees out of phase.

See:
http://scienceworld.wolfram.com/physics/ConstructiveInterference.html
http://scienceworld.wolfram.com/physics/DestructiveInterference.html

The formulas you provided are actually not specifically for maximum constructive interference (MCI) and perfect destructive interference (PDI), but rather represent the general formula for calculating the phase difference, denoted as Δφ, between two interfering waves. The concept of interference involves the combination of waves from different sources or parts of the same source, resulting in either reinforcement (constructive interference) or cancellation (destructive interference) of the waves.

To understand MCI and PDI in the context of interference, let's clarify the formulas:

For Constructive Interference:
Δφ = 2π(deltax/λ) + Δφ

For Destructive Interference:
Δφ = (2n + 1)π/2 + Δφ

In both formulas, Δφ represents the phase difference between the interfering waves, deltax is the path difference (the difference in distances traveled by the waves), and λ is the wavelength of the waves. The Δφ term in the formulas accounts for any additional phase shift that exists between the interfering waves, such as from reflections or different sources.

Now, in order to determine the conditions for MCI and PDI, we need to consider the specific values of the phase difference.

For MCI:
The condition for MCI occurs when the phase difference Δφ is an integer multiple of 2π (0, ±2π, ±4π, etc.), which means the waves are in phase or nearly in phase. This occurs when:
2π(deltax/λ) + Δφ = 2πn (where n is an integer)

For PDI:
The condition for PDI happens when the phase difference Δφ is an odd multiple of π/2 (±π/2, ±3π/2, ±5π/2, etc.), indicating that the waves are completely out of phase. This occurs when:
(2n + 1)π/2 + Δφ = mπ (where n and m are integers)

Remember that the Δφ term takes into account any additional phase shifts caused by specific factors, like reflection or sources with different initial phases.

By utilizing these formulas and conditions, you can determine the path difference or phase difference required for either MCI or PDI during interference experiments.