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A stationary helium ion emits a photon corresponding to the first line of Lyman series. That photon liberates a photoelectron form a stationary hydrogen atom in ground state. Find the velocity of photoelectron. Take mass of electron `=9.11xx10^(-31)kg` and ionisation energy of hydrogen atom=13.6ev. |
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Answer» We neglect recoil effects. The energy of the first Lyman line photon emitted by `He^(+)` is `4 ħR(1-(1)/(4))=3 ħR` The velocity `v` of the photoelectron that this photon liberates is given by `3 ħR=(1)/(2)mv^(2)+ ħR` where ` ħ R` on the right is the binding energy of the `n=1` electron in `H` atom. Thus `v=sqrt((4 ħR)/(m))=2sqrt(( ħR)/(m))=3.1xx10^(6)m//s` Here `m` is the mass of the direction. |
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