13.14. Atomic nucleus, isotopes, radiation

Question 1

What is an isotope?

Answer 1

same atomic number, different atomic mass number (same number of protons and electrons but different neutrons)

Question 2

What is the N/Z ratio?

Answer 2

neutron / proton ratio : generally increases with increasing atomic number

Question 3

What is beta decay?

Answer 3

occurs during transformation of a particle contained in the atomic nucleus and emission of multiple particles

Question 4

What is beta minus decay?

Answer 4

surplus of neutrons, turns into 1 positron and emits 1 electron and an antineutrino

Question 5

What is gamma decay?

Answer 5

unstable atomic nuclei dissipates excess energy bu spontaneous electromagnetic process : releases high E photon after alpha or beta radiation

Question 6

What is the energy range of gamma decay photons?

Answer 6

keV-MeV

Question 7

What ate the 2 artificial ways to produce isotopes?

Answer 7

via accelerator (charged nuclei strike) or via reactors (neutron flux)

Question 8

What is an isomeric transition?

Answer 8

When there is delay in the emission of gamma photon because there is a metastable state in the “daughter nucleus”

Question 9

What is the minimal energy required for pair production and why?

Answer 9

1.022 MeV : 2x511kEV, because the photon must have more energy than the sum of the rest mass energies

Question 10

What is the definition of activity?

Answer 10

the amount of decays in a unit time

Question 11

What is the unit of activity?

Answer 11

Bequerel : 1 decay/s

Question 12

What is the decay constant?

Answer 12

probability of the decay 1/s

Question 13

Which particles can directly ionize matter?

Answer 13

particles with electric charge

Question 14

Which particles cannot directly ionize matter?

Answer 14

uncharged particles (photons)

Question 15

How does the alpha particle interact with matter?

Answer 15

directly ionize atoms of matter by coulomb’s force. Short effective range bc heavy : low penetration depth

Question 16

How does the beta minus particle interact with matter?

Answer 16

small charged particle : directly ionizes atoms of matter by coulomb force. since smaller and less charge, it penetrates ore than alpha particles

Question 17

How does the beta plus particle interact with matter?

Answer 17

undergoes annihilations

Question 18

What is neutron radiation?

Answer 18

a form of ionization radiation that presents as free neutrons

Question 19

How does neutron radiation happen?

Answer 19

• collision with nucleus
• nuclear fission / fusion : release of neutrons
• may lead to propagation (triggers more neutron radiation)

Question 20

Why can proton radiation be precisely radiated?

Answer 20

because its radiation dose peaks and then decreases completely instead of X-rays where it decreases progressively

Question 21

What is the Bragg curve?

Answer 21

plots the energy loss of radiation during its travel through matter. Radiation dose vs penetration depth

Question 22

What is the Bragg peak?

Answer 22

where the maximum dose is achieved