The energy that should be added to an electron to reduce its de - Broglie wavelength from one `nm to 0.5 nm` is

Options

A. four times the initial energy
B. equal to the initial energy
C. twice the initial energy
D. thrice the initial energy

Answer

D

Explanation

(d) : As `lamda=(h)/(sqrt(2mE)) or E=(h^(2))/(2mlamda^(2))i.e.Eprop(1)/(lamda^(2))`
or `(E^('))/(E)=(lamda^(2))/((lamda^('))^(2))=((1)/(0.5))^(2)=4 or E^(')=4E`
The energy should be added to decrease the wavelength
`=E^(')-E=4E-E=3E`