Radioactivity Ch. 2

Question 1

When a radionuclide decays, radiation is emitted from the:
A. Outer orbital electrons of the atom
B. Innermost shell of the atom
C. The nucleus of the atom
D. All of the above

Answer 1

C. The nucleus of the atom

Question 2

The half-life of a radionuclide is the time required to reduce:
A. The volume of the isotope into half
B. The number of radioactive atoms to half of their initial number
C. The activity to half of its initial value
D. B and C are true
E. A, B, C all are true

Answer 2

D. B and C are true

Question 3

If the activity in a sample of radionuclide is 100 mCi, how many half-lives would be
required for it to decay to less than 2 mCi:
A. 3
B. 4
C. 5
D. 6

Answer 3

D. 6

Question 4

Samples of two radionuclides with different half-lives initially contain the same
number of radioactive nuclei. The sample with the longer half-life will have:
A. A shorter biological half-life
B. A longer average life time
C. Produce a higher exposure rate
D. A higher activity

Answer 4

B. A longer average life time

Question 5

The disintegration constant lambda (λ) is equal to:
A. Physical half-life x 1.44
B. Biological half-life x .0693
C. Physical half-life x 0.693
D. 0.693 / physical half-life

Answer 5

D. 0.693 / physical half-life

Question 6

The dose delivered to an internal organ is a function of:
A. Organ uptake
B. Activity administered
C. Biological half-life
D. Physical half-life
E. All of the above

Answer 6

E. All of the above

Question 7

Specific activity of a radionuclide refers to:
A. Number of disintegrations per second
B. Number of grams per Ci
C. Activity per unit mass
D. Number of atoms per centimeter cube

Answer 7

C. Activity per unit mass

Question 8

If the specific activity in a sample decreases, its:
A. Half-life decreases
B. Physical life increases
C. Activity per gram of the material decreases
D. All of the above

Answer 8

C. Activity per gram of the material decreases

Question 9

The physical half-life of a radionuclide is:
A. The same as the average life
B. Less than the average life
C. Directly proportional to the decay constant
D. Reciprocal of biological half-life

Answer 9

B. Less than the average life

Question 10

After 5 half lives, the fraction of initial activity is reduced to:
A. One-fifth
B. One-fifth to the power of 2
C. Square root of ½
D. ½ to the power of 5

Answer 10

D. ½ to the power of 5