Significance of n = ∞

First of all, it is just a symbol for the concept of growing without bound. Instead of saying "let x (or n) grow without bound", mathematicians often say "let x (or n) tend to infinity" or "as x (or n) tends to infinity". There is a special shorthand for this, too: x → ∞ (or n → ∞).

Explanation:

1 - wave length

2 - amplitude

3 - crest

4 - trough

explanation:

duh.

a displacement distance is size of displ