Q.

The ratio of momentum of the photons of the 1st and 2nd line of Balmer series of Hydrogen atoms is αβ. The possible values of α and β are            [2026]

1 27 and 20  
2 3 and 16  
3 5 and 36  
4 20 and 27  

Ans.

(4)

The momentum of a photon  p=hλ

The Rydberg formula for hydrogen (Z=1)

        1λ=R(1n12-1n22)

For the 1st line (3→2)

1λ1=R(122-132)=R(14-19)=R(536)

For the 2nd line (4→2)

1λ2=R(122-142)=R(14-116)=R(316)

∴  Ratio P1P2=1/λ11/λ2=R(5/36)R(3/16)=2027

α=20 and β=27