(i) State Bohr's quantisation condition for defining stationary orbits. How does de-Broglie hypothesis explain the stationary orbits ?
(ii) Find the relation between the three wavelengths, `lambda_(1),lambda_(2)` and `lambda_(3)` from the energy level diagram shown here.

Explanation

(i) See Short Answer Question Number 29.
(ii) Let energy of electron corresponding to levels A, B and C by `E_(A)` , `E_(B)` and `E_(C)` respectively . Then
`E_(C) - E_(B) = (hc)/(lambda_(1)) " "…(i) E_(B) =E_(A) = (hc)/(lambda_(2)) " "......(ii) and E_(C) -E_(A) =(hc)/(lambda_(3))" ".......(iii) `
On adding (i) and (ii) , we get .
`E_(C) = E_(A) = (hc)/(lambda_(1)) + (hc)/(lambda_(2))" ".......(iv)`
Now comparing (iii) and (iv) , we find that .
`(1)/(lambda_(3)) = (1)/(lambda_(1)) + (1)/(lambda_(2))`