Nuclear physics

Which nuclide is the most stable?

• calcium-40

• hydrogen-1

• iron-56

• carbon-12

Which shows correctly the calculation of mass defect of a nucleus?

• (mass of nucleus) − (total mass of separate neutrons)

• (total mass of separate neutrons) − (mass of nucleus)

• (mass of nucleus) − (total mass of separate nucleons)

• (total mass of separate nucleons) − (mass of nucleus)

What is meant by binding energy?

• minimum energy required to separate nucleons in a nucleus to infinity

• maximum energy required to separate nucleons in a nucleus to infinity

• minimum energy required to remove one nucleon from a nucleus

• maximum energy required to remove one nucleon from a nucleus

Uranium-235 has 92 protons and a binding energy of 1786 MeV. Calculate its binding energy per nucleon.

• 19.4 MeV

• 7.6 MeV

• 12.5 MeV

• 0.13 MeV

Which of the following statements is wrong?

• Activity is the number of decay per unit time.

• Activity depends on half-life.

• Activity depends on decay constant.

• Activity can measured directly using a GM tube.

A house is found to have high level of radon gas. The acitivity is 2000 Bq per unit cubic metre of air. The action level recommended by UK is 200 Bq/m³. How long does it take for activity to fall below the action level if there is no influx of more radon gas? (half life of radon = 3.8 days.)

• 13 days

• 19 days

• 23 days

• 10 days

Which of the following equations about activity (A), count rate (R), and number of undecayed nuclei (N) are correct?

•  $A=A_0e^{\lambda t}$  

•  $R=R_0e^{-\lambda t}$ 
  

•  $N=N_0e^{\lambda t}$ 

•  $N=N_0e^{-\lambda t}$ 

A sample of cobalt-60 has a mass of 8.84×10⁻¹⁰ g and activity of 3.7×10⁴ Bq. What is the half-life of cobalt-60? (N_A=6.02×10²³; u=1.66×10⁻²⁷ kg.)

• 5.27 days

• 5.27 years

• 52.7 years

• 527 years

Which of the following cause measured count rate to be different than activity? (Select all.)

• Detector has dead time.

• Radiation is absorbed by the sample.

• Detector has 100% efficiency.

• Detector covers sample fully.

• There is background radiation.

Which of the following steps is NOT required when measuring half-life of radioisotope that is extremely long-lived?

• Measure number of parent nuclei

• Plot activity against time
  

• Use  $A=\lambda N$ 

• Measure activity