4 - Nuclear Physics Questions Answers
the half life of radium is 1620 year & its atomic weight is 226gm/mole. the number of atoms that will decay from its 1g sample per second is
1) 3.16 x 1010
2)3.6 x 1012
3) 3.1 x 1015
4) 31.1 x 1015
for radioactivity we know that it is a first order process
so dN/dt = -λN
so dN/1 = -[0.6932/(1620*3.1*107)]*(1/226)*6.023*1023
solve now
A RADIOACTIVE SUBSTANCE EMITS n BETA PARTICLES IN THE FIRST 2 SECONDS & 0.5 n BETA PARTICLES IN THE NEXT 2 SECONDS . THE MEAN LIFE OF THE SAMPLE IS
ANS 2/(ln2) s
A RADIOACTIVE SUBSTANCE EMITS n BETA PARTICLES IN THE FIRST 2 SECONDS & 0.5 n BETA PARTICLES IN THE NEXT 2 SECONDS. Definitely by definition its half life will be 2 sec.
so mean life = half life / ln2 This is the relation between mean life and half life.
A NUCLEUS OF MASS NO. 220, INITIALLY AT REST , EMITS AN .α PARTICLE . IF THE Q VALUE OF THE Rxn IS 5.5MeV THE ENERGY OF THE EMITTED α PARTICLE WILL BE ??
ANS 5.4 MeV
5.5*216/220 = 216/40 = 5.4 MeV here 216 is the mass of nucleus after ejecting α particle.
The activity of a freshly prepared radioactive sample is 10^10 disintegrations per second, whose mean life is 10^9 sec.
The mass of an atom of this radioisotope is 10 ^ -25 kg. The mass (in mg) of the radioactive sample is
dN/dt = -λN
1010 = -[1/109] N λ = 1/mean life
so N = 1019 disintegration
so mass of radioisotope = 1019 *10-25 = 10-6 Kg = 1 mg