Q.

Electron beam used in an electron microscope, when accelerated by a voltage of 20 kV, has a de-Broglie wavelength of λ0. If the voltage is increased to 40 kV, then the de-Broglie wavelength associated with the electron beam would be                 [2023]

1 λ02  
2 3λ0  
3 λ02  
4 9λ0  

Ans.

(3)

λ=h2mVq

λλ0=2040  λ=λ02