If the de-Broglie wavelength of an electron beam is `5xx10^(-10)` m, then what is the retarding potential (in volt) necessary to completely stop the beam. (Round off to nearest integer)

Answer

`6`

Explanation

`p=h/lambda=(6.6xx10^(-34))/(5xx10^(-10)) = 1.32xx10^(-24)`
`E=p^(2)/(2m)=qV`
`((1.32xx10^(-24)1)^(2))/(2xx9xx10^(-31)xx1.6xx10^(-19))=V`
`=(1.32xx1.32xx10^(-48))/(18xx1.60xx10^(-50))=(132xx132)/(18xx160)=121/20=6.05 V approx 6V`