Nuclei

Which of the following statements correctly explains why nuclear energy is much larger than chemical energy?

1. Chemical reactions involve larger mass defects.
2. Nuclear reactions involve conversion of a measurable amount of mass into energy according to E = mc².
3. Nuclear reactions involve only electrons.
4. Chemical reactions occur at higher temperatures.

A radioactive sample has an initial activity of 1600 disintegrations per second. If its half-life is 4 hours, what will be its activity after 12 hours?

1. 800 disintegrations per second
2. 400 disintegrations per second
3. 200 disintegrations per second
4. 100 disintegrations per second

The energy released in nuclear fusion is mainly due to:

1. Decrease in atomic number
2. Increase in mass defect and binding energy per nucleon
3. Decrease in binding energy
4. Emission of electrons

Which one of the following reactions is an example of nuclear fission?

1. H-2 + H-3 → He-4 + n + Energy
2. U-235 + n → Ba-141 + Kr-92 + 3n + Energy
3. C + O2 → CO2
4. HCl + NaOH → NaCl + H2O

Which of the following nuclei is expected to have the highest binding energy per nucleon?

1. Hydrogen-1
2. Helium-4
3. Iron-56
4. Uranium-238

Which of the following statements about gamma radiation is correct?

1. It consists of helium nuclei.
2. It consists of high-speed electrons.
3. It is electromagnetic radiation with no charge.
4. It consists of protons.

During alpha decay, the atomic number and mass number of the parent nucleus change respectively by:

1. -1 and 0
2. -2 and -4
3. +2 and +4
4. 0 and -1

The mean life of a radioactive substance is 20 days. Its decay constant is:

1. 0.05 day^(-1)
2. 0.0347 day^(-1)
3. 0.693 day^(-1)
4. 20 day^(-1)

Which of the following represents beta-minus decay correctly?

1. X(A,Z) → Y(A-4,Z-2) + He(4,2)
2. X(A,Z) → Y(A,Z+1) + e(-1,0) + antineutrino
3. X(A,Z) → Y(A,Z-1) + positron
4. X(A,Z) → Y(A,Z) + gamma

The mass defect of a nucleus is 0.20 u. The binding energy of the nucleus is approximately: (Given: 1 u = 931.5 MeV)

1. 93.15 MeV
2. 186.3 MeV
3. 279.45 MeV
4. 465.75 MeV

The radius of a nucleus is proportional to:

1. A
2. A^(1/2)
3. A^(1/3)
4. A^2

The relation between decay constant (lambda) and half-life (T1/2) is:

1. T1/2 = λ/0.693
2. T1/2 = 0.693/λ
3. λ = 0.693 × T1/2
4. λ = 1/T1/2

Which of the following radiations has the greatest penetrating power?

1. Alpha rays
2. Beta rays
3. Gamma rays
4. All have the same penetrating power

The half-life of a radioactive substance is 8 days. The fraction of the original sample remaining after 24 days is:

1. 1/2
2. 1/4
3. 1/8
4. 1/16

The binding energy of a nucleus is 1863 MeV and its mass number is 207. The binding energy per nucleon is closest to:

1. 7.0 MeV
2. 8.0 MeV
3. 9.0 MeV
4. 10.0 MeV