1.4 - Particles & antiparticles

Question 1

what is the same between corresponding particles and antiparticles

what is different

Answer 1

• same rest energy
• opposite charge

Question 2

Describe B+ decay

• give equation

Answer 2

P+ –> n and a positron is emitted alongside a neutrino

^A _ZX –> ^A_Z-1Y + ⁰₊₁B + V

Question 3

What are all positron emitting isotopes

Answer 3

man-made / unnatural

Question 4

How are positron-emitting made

Answer 4

placing stable isotopes (in sold / liquid form) in the beam of high impact protons

nuclei absorb P+, becoming unstable isotopes, positron emitters

Question 5

Give a use of positron-emitting isotopes

(give full name too)

Answer 5

PET scanners

(positron emitting tomography)

Question 6

Describe how PET scanners work

Answer 6

• position emitting isotope injected into the bloodstream and starts breaking down at the desired organ
• The e+ annihilate the e- inside your body, producing 2 gamma photons
• the distances each photon travels to hit the doctor alongside time is used to generate an image

(no detection = lack of blood flow to a certain area, creates an empty space on image)

Question 7

describe anhiliation

Answer 7

when a particle and antiparticle collide, their masses are converted into energy in the form of 2 gamma photons

Question 8

annihilation diagram and overall equation

Answer 8

2 hf_min = 2E₀

(min energy of both gamma photons) = (rest energy of particle & antiparticle pair)

Question 9

what is the opposite process of annihilation

Answer 9

pair production

Question 10

describe pair production

Answer 10

when a photon with a high enough rest energy to split into a particle and antiparticle pair

energy converted into matter

photon must pass near an e- or nuclei

Question 11

pair production diagram and overall equation

Answer 11

hf_min = 2E₀

Question 12

convert 1 eV into J

Answer 12

1 eV x 1.6x10^-19 = 1.6x10^-19 J

(times by e- charge!)

Question 13

convert 1 MeV into J

Answer 13

M = mega, 1x10⁶

1 MeV = 1.6x10^-13 J

(1. 6x10^-19 x 1x10⁶ = 1.6x10^-13)
- electron carge X million

Question 14

Discovery of positron

• diagram + description

Answer 14

Ionization particle sent through a saturated area containing cold vapor. particle leaves a visible trail behind (liquid droplets)

• has a magnetic field around it (larger / slower particles = larger curve), unlike charges went in opposit direction.

a particle did the same thing as an e- but bent in the other direction (same size, diff charge = positron)