Whats the meaning of these lines:the angular momentum can have values such ash/2π,2h/2π,3h/2π….,etc.but it cannot have a fractional value.

net torque is zero during circular moiton due to presence of only central forces as a result angular momentum is conserved.
ang mom=(mv)r=pr=hr/(lambda)
now the wavelenth must be a part of the circumferance 2(pi)r/n
putiing the value.
ang mom=nh/2pi

According to Bohr''s second postulate, the electrons revolving in nuclear orbits of principal quantum numbers ''n'' can have only those values of angular momentum which are integral multiples of h/2p (i.e. mvr = nh/2p) . Therefore, fractional values of angular momentum are not allowed.  

We know that anugalar momentum can have value n*h/2*pie where n is a integer..so fractinaol values nt allowed

It means that angular momentum of an electron cannot just take any value. It is specific for different shells. It assume only dicreet values and thus the angular momentum of an electron is quantisized:

Angular momentum=mvr=nh/2pi

what havnt u undertood...??? u disapproved it!??
was it the wavelenght=2pie r/n ??
ok heres it :- the (wavelenght) .(a natural no.)=total circumference=2.pie.r
[this must be satisfied in order the electron''s orbit is completed]
hence,ang. mom.=nh/2pi
it depicts the ang mom. can only take integral values of h/2.pi
Plz approve

According to Bohr''''s second postulate, the electrons revolving in nuclear orbits of principal quantum numbers ''''n'''' can have only those values of angular momentum which are integral multiples of h/2p (i.e. mvr = nh/2p) . Therefore, fractional values of angular momentum are not allowed.

 angular momentum of electron in orbit is multiple of nH/2∏

where n is prinipal quantum number