1.

Calculate the de Broglie wavelength of an electron that has been accelerated from rest through a potential difference of 1 keV.

Answer»

Solution :`gamma =h/(mv)`
Potendial difference of an ELECTRON=V=1keV.
`THEREFORE "Potential energy "=1/2mv^(2)=eV`
e=charge of an electron=`1.609xx10^(-19)c`
`kv=1000V`
`therefore "Potential energy"=1.609xx10^(-19)xx1000`
`=1.609xx10^(-16)`
`1/2mv^(2)=1.609xx10^(16)V``m=9.1xx10^(-31)kg`
`gamma=h/(mv)`
`v^(2)=(2xx1.609xx10^(-16))/(9.1xx10^(-31))`
`v=sqrt(2xx1.609xx10^(-16))/(9.6xx10^(-31)`
=`5.9xx10^(7)ms^(-1)`
`gamma=h/(mv)=(6.626xx10^(-34))/(9.1xx10^(-31)xx5.93xx10^(7))`
`=1.2xx10^(11)m`
`gamma=1.2xx10^(-11)m`


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