Q.

An electron projected perpendicular to a uniform magnetic field B moves in a circle. If Bohr quantization is applicable, then the radius of the electronic orbit in the first excited state is:         [2025]

1 2hπeB  
2 4hπeB  
3 h2πeB  
4 hπeB  

Ans.

(4)

mvr=nh2π                        ...(i)

r=vmBq                              ...(ii)

n = 2

mr(rBqm)=2h2π  r=hπBq

q=e  r=hπBe