Q.

An electron in the ground state of the hydrogen atom has the orbital radius of 5.3×1011 m while that for the electron in third excited state is 8.48×1010 m. The ratio of the de-Broglie wavelengths of electron in the ground state to that in excited state is          [2025]

1 4  
2 9  
3 3  
4 16  

Ans.

(1)

According to de-Broglie hypothesis, λ=hmv

mvr=nh2π  mv=nh2πr

λ=2πrhnh  λrn

λ1λ4=r1n4n1r4=5.3×1011×41×84.8×1011

 λ1λ4=14

Note: Most appropriate answer will be option (1).