1.

A nucleus of amss 20 u emits a gamma photon of energy 6 MeV . If the emission assume to occur when nuclues is free and at rest then the nulceus will have kintetic energy nearest to (take 1u=1.6xx10^(-27)Kg)

Answer»

10 KeV
1 KeV
0.1 KeV
100 KeV

Solution :By conservation of linear MOMENTUM
Momentum of photon = momentum of NUCLEUS
`(E)/(c )=sqrt(2m(KE))`
`(6xx10^(6)xx1.6xx10^(-19))/(3xx10^(8))=sqrt(2xx20xx1.6xx10^(-27)xxKE)`
`3.2xx10^(-21)=sqrt(64xx10^(-27)xxKE)`
`((3.2)^(2)xx10^(-42))/(64xx10^(-27))=KE`
`KE=1.6xx10^(-16)J`
`KE=(1.6xx10^(-16))/(1.6xx10^(-19))eV=10^(3)eV=1keV`


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