Q.

An electron with mass 'm' with an initial velocity (t=0)v=v0i^(v0>0) enters a magnetic field B=B0j^. If the initial de-Broglie wavelength at t = 0 is λ0 then its value after time 't' would be:          [2025]

1 λ01e2B02t2m2  
2 λ01+e2B02t2m2  
3 λ01+e2B02t2m2  
4 λ0  

Ans.

(4)

Speed does not change due to magnetic field, that's why λdebroglie remains unchanged.