Which Formula Correctly Represents the Kinetic Orbital Momentum of an Electron?

[C_Ovidiu]

In some places I saw that the module of the kinetic orbital momentum of an electron in an atom is
a) L^2=l(l+1)h^/(4pi^2) ==> L =h/(2pi)sqrt(l*(l+1)) l=0,1,2,...n-1
b) L=n*h/(2pi)
n beeing the energy level of an electron .

Now , my opinion is that the first is true . But I saw some problems solved using only the second value . I'm really confused . Which one is it ?
Thank you !

 

[dextercioby]

Well, the first equation comes from the angular momentum theory in quantum mechanics, while the second is nothing but one of Bohr's postulates in his 1913 theory of the hydrogen atom.

Do you see what the difference is really about ?

 

[C_Ovidiu]

Tks .
There are lots of differences .