Electrons used in an electron microscope are accelerated by a voltage of 25 kV. If the voltage is increased to 100 kV then the de Broglie wavelength associated with the electrons would

Options

A. increase by 2 times
B. decrease by 2 times
C. decrease by 4 times
D. increase by 4 times

Answer

B

Explanation

The de broglie wavelength `lamda` associated with the electrons is
`lamda=(1.227)/(sqrt(V))nm`
where V is the accelerating potential in volt.
or `lamdaprop (1)/(sqrt(V))`
`therefore(lamda_(1))/(lamda_(2))=sqrt((100xx10^(3))/(20xx10^(3)))=2`
or `lamda_(2)=(lamda_(1))/(2)`