Nuclei

The decay constant of a radioisotope is . If A1 and A2 are its activities at times t1 and t2 respectively, the number of nuclei which have decayed during the time (t1 - t2)

1. A1t1 - A2t2
2. A1 - A2
3. (A1 - A2)/
4. (A1 - A2)

The mass of a 73Li nucleus is 0.042 u less than the sum of the masses of all its nucleons. The binding energy per nucleon of 73Li nucleus is nearly

1. 46 MeV
2. 5.6 MeV
3. 3.9 MeV
4. 23 MeV

The activity of a radioactive sample is measured as N0 counts per minute at t = 0 and N0/e counts per minute at t = 5 minutes. The time (in minutes) at which the activity reduces to half its value is

1. e 25
2. 5 e 2
3. 5 10 2
4. 5 e 2

In the nuclear decay given below AZX AZ+1Y A-4Z-1 B* A-4Z-1B, the particles emitted in the sequence are

1. , ,
2. , ,
3. , ,
4. , ,

The number of beta particles emitted by a radioactive substance is twice the number of alpha particles emitted by it. The resulting daughter is an

1. isomer of parent
2. isotone of parent
3. isotope of parent
4. isobar of parent

If M(A, Z), Mp and Mn denote the masses of the nucleus AZX, proton and neutron respectively in units of u (1 u = 931.5 MeV/c2) and BE represents its binding energy in MeV, then

1. M(A, Z) = ZMp + (A - Z)Mn - BE
2. M(A, Z) = ZMp + (A - Z)Mn + BE/c2
3. M(A, Z) = ZMp + (A - Z)Mn - BE/c2
4. M(A, Z) = ZMp + (A - Z)Mn + BE

Two nuclei have their mass numbers in the ratio of 1 : 3. The ratio of their nuclear densities would be

1. (3)1/3 : 1
2. 1 : 1
3. 1 : 3
4. 3 : 1

Two radioactive materials X1 and X2 have decay constants 5 and respectively. If initially they have the same number of nuclei, then the ratio of the number of nuclei of X1 to that of X2 will be 1e after a time

1. 14
2. e
4. 12

A nucleus AZX has mass represented by M(A, Z). If Mp and Mn denote the mass of proton and neutron respectively and B.E. the binding energy in MeV, then

1. B.E. = [ZMp + (A - Z)Mn - M(A, Z)]c2
2. B.E. = [ZMp + AMp - M(A, Z)]c2
3. B.E. = M(A, Z) - ZMp - (A - Z)Mn
4. B.E. = [M(A, Z) - ZMp - (A - Z)Mn]c2

Two radioactive substances A and B have decay constants 5 and respectively. At t = 0 they have the same number of nuclei. The ratio of number of nuclei of A to those of B will be ( 1e )2 after a time interval

1. 4
2. 2
3. 12
4. 14