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Determine the de Broglie wavelength of a proton, whose kinetice energy is equal to the rest of the mass energy of an electron. Given that the mass of an electron is `9xx10^(-31)` kg and the mass of a proton is `1837` times as that of the electron.

Answer» Here mass of electron, `m_0=9.1xx10^(-31)`kg
Mass of proton, `m=1837xx9.1xx10^(-31)=1.67xx10^(-27)`kg
let v be the velocity of the proton. Then,
`(1)/(2)mv^(2)=m_0c^(2)`
or `m^(2)v^(2)=2mm_0c^(2)`
or `mv=sqrt(2mm_0c)`
`=sqrt(2xx1.67xx10^(-27)xx9.1xx10^(31))xx3xx10^(8)`
`=1.654xx10^(20)kgms^(-1)`
Threfore, de Broglie wavelength of the proton,
`lamda=(h)/(mv)=(6.62xx10^(-32))/(1.654xx10^(-20))=4xx10^(-14)m`


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