Page 3 - LN 5

circumference of the orbit must be equal to an integral

multiple of wavelength λ, i.e,
2ᴫr = n λ ………………..(1)

λ = h/mv
Putting this value I equation 1 we have

2ᴫr = nh/mv

mvr =nh/2ᴫ,which is Bohr's postulate of angular momentum.

 Heisenberg's Uncertainty Principle :
STATEMENT :

It is impossible to determine simultaneously, the exact position and
exact momentum (or velocity) of an electron.
i.e. The product of the uncertainty in the position(∆x) and the
uncertainty in the momentum(∆p) is always constant and is equal to or
greater than h/4ᴫ.
Mathematically it can be written as
h

 x . p 
4 
We know that ∆p = m.∆v

Putting this value in above equation we have

h
 x. m v 
4 
h
 x. v 
4  m
 Significance :It is of significance only for microscopic particles.