# Ladder Operators - I need help.

#### Pmb

PHF Hall of Fame
I can't see his justification of Eq. [2.63] on page 47. I know its true but long ago forgot why and I can't see Griffith writing anything to justify it. Help/thoughts?

#### benit13

I can't see his justification of Eq. [2.63] on page 47. I know its true but long ago forgot why and I can't see Griffith writing anything to justify it. Help/thoughts?
I think it's considered as a consequence of Eq. 2.61, which shows that the next/previous wave function in the ladder is obtained by applying the operator and renormalising. Therefore, the proportionality constant, $$\displaystyle c_n$$, is just the inverse of $$\displaystyle A_n$$, repurposed for the algebraic method. Considering how $$\displaystyle c_n$$ is linked to $$\displaystyle A_n$$, it is unsurprising, then, that the result is a square root of a factorial.