Antimatter

And Annihilation

Remember Photons?

• What are photons?

What can Photons do?

• When photons come close to an atom, they can do a few things:

• 1) NOTHING- it just sails by and doesn’t hit anything

What can Photons do?

• When photons come close to an atom, they can do a few things:

• 2) It can hit an electron and make it go up a level…

What can Photons do?

• When photons come close to an atom, they can do a few things:

• 3) It can knock an electron loose (Remember the photoelectric effect?)

What can Photons do?

• When photons come close to an atom, they can do a few things:

• 4) If it had A LOT of energy, it can spontaneously turn into matter!

Poof!

e-

e+

BIG PHOTON

What can Photons do?

• But not just anything…..• The huge photon can spontaneously create an electron and a positron.

Poof!

e-

e+

BIG PHOTON

electron

positron

MATTER

What can Photons do?

• Electrons are regular electrons.• Positrons are special particles that are called ANTIMATTER! (Like the Red Matter in the Star Trek Movie)

Positrons

• Positrons are created very rarely and don’t live very long.

• They are exactly like an electron BUT, they have a positive charge! (They even have the same mass as an electron)

Positrons

• So…

• Electrons PositronsMass 9.11E-31kg 9.11E-31kgCharge Neg (-) Pos (+)

Matter Antimatter

e- e+

Einstein’s Equation

• So how much energy does the photon need to be in order to create these two particles?

• Einstein figured it out…

2mcE

Einstein’s Equation

2mcE Energy Needed

Total mass created

Speed of light squared

s

mEc 800.3

Example

• What is the minimum energy needed for a photon to create an electron-positron pair? Recall the mass of both particles is 9.11E-31kg.

Example

• What is the minimum energy needed for a photon to create an electron-positron pair? Recall the mass of both particles is 9.11E-31kg.melectron=9.11E-31kg

mpositron=9.11E-31kg

Example

• What is the minimum energy needed for a photon to create an electron-positron pair? Recall the mass of both particles is 9.11E-31kg.melectron=9.11E-31kg

mpositron=9.11E-31kgJEE

EEEs

mEkgEkgEE

mcE

136398.1

)1600.9)(30822.1(

)800.3)(3111.93111.9( 2

2

Antimatter

• So when you get a lot of high energy photons, you have a chance of creating some matter and antimatter both at the same time.

HOWEVER….

• If antimatter runs into regular matter after its’ created, something else happens….

Antimatter

MatterAntimatter

Antimatter

MatterAntimatter

Antimatter

MatterAntimatter

Antimatter

MatterAntimatter

Antimatter

KABOOM!!

BIG EXPLOSION: All the energy that was needed to create the particles in the first place is released all over again.

This KABOOM is called Annihilation.

Example

• How much energy is released when .005kg of dirt annihilates with .005kg of anti-dirt. Anti-dirt is just dirt made up of antimatter particles.

Example

• How much energy is released when .005kg of dirt annihilates with .005kg of anti-dirt. Anti-dirt is just dirt made up of antimatter particles.

mtotal=.005kg+.005kg=.010kg2mcE

Example

• How much energy is released when .005kg of dirt annihilates with .005kg of anti-dirt. Anti-dirt is just dirt made up of antimatter particles.

mtotal=.005kg+.005kg=.010kg

JEE

EkgE

smEkgE

mcE

149

)1600.9)(010(.

)/800.3)(010(. 2

2

Practice

• Complete the worksheet on antimatter creation and annihilation.