Question

How are maxima and minima formed?

Answer 1

Local maxima and local minima:

Maxima and minima of a function are the largest and smallest value of the function respectively either within a given range or on the entire domain.

Collectively they are also known as extrema of the function. The maxima and minima are the respective plurals of maximum and minima of a function.

When $f\text{'}\left(x\right)$ chnage sign from positive to negative, then it will form maxima and When $f\text{'}\left(x\right)$ chnage sign from negative to positive , then it will form minima.

Hence, maxima and minima are formed when the path difference between the waves is a whole number of wavelengths or when an odd number of half wavelengths respectively.