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Physic > Particle Physics > Flashcards

Particle Physics Flashcards

1
Q

When a positron an electron meet two photons are produced. Write down an equation to represent this interaction.

A

e^+ + e^- –>2y

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2
Q

Why are photons produced when a positron & an electron meet?

A

Mass converts into energy

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3
Q

Why are two photons produced in the collision between an electron and a positron?

A

To conserve momentum

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4
Q

How to calculate the minimum frequency of the photons produced

A

E=hf & E=mc^2
hf=mc^2
Back of tables p.46
Mass of an electron

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5
Q

Explain why the photons produced in this collision of an electron and proton, usually have a greater frequency than your calculated minimum frequency value

A

Colliding particles have kinetic energy

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6
Q

Why must two positrons travel at high speeds to collide with each other?

A

Because they repel each other

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7
Q

How are charged particles given high speed?

A

Particle Accelerator
Cyclotron
Electric field for acceleration purposes

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8
Q

What are magnetic fields used for in a particle accelerator

A

Magnetic fields are used to confine And control the position of the particle beams

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9
Q

What are electric fields used for in a particle accelerator

A

Electric fields are used repeatedly for accelerating purposes

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10
Q

Explain why to positrons cannot annihilate(ruin or destroy) each other in a collision

A

In conflict with conservation of charge

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11
Q

How did Cockroft and Walton accelerate the protons

A

By using high-voltage plates

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12
Q

How did they detect the alpha-particles

A

Light flashed as it hit the zinc sulphide screen

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13
Q

What is a positron?

A

Positron is a positively charged electron

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14
Q

Write the nuclear equation from the reaction that occurred in Cockcroft& Walton’s experiment

A

73Li+11H–>42He+42He

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15
Q

What is the historical significance of their (cockrofts&waltons)observation

A

This was the first ever experiment conducted a proved E=mc^2

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16
Q

In particle Accelerators they have an evacuated tube, why?

A

So that the particles do not collide with anything

So it has a free Way and can accelerate

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17
Q

What is the purpose of accelerating the particles to have a high velocity?

A

So more energy is produced which when they collide with other particles may form to create new particles

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18
Q

What is the purpose of the magnets in the particle Accelerator

A

To control the position of the particle beam

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19
Q

Give an advantage of a circular accelerator over linear accelerator

A

Takes up less space

Particles can achieve greater energy and so increase their speed

20
Q

Can you a particle accelerator be used to accelerate neutrons?

A

No because neutrons have no charge and so are not affected by the electric or magnetic fields

21
Q

List three quantities that are conserved in nuclear reactions

A

Momentum
Charge
Mass-energy
Nucleons

22
Q

Write an equation for a nucleus undergoing beta-decay

A

228/88X –> 228/89Y + 0/-1 e

23
Q

In initial observations of beta-decay, not all three quantities appear to be conserved. What was the solution to this contradiction?

A

The discovery of the Neutrino

24
Q

List the fundamental forces of nature in increasing order of their strength

A
  1. Gravitational force
  2. Weak nuclear force
  3. Electromagnetic force
  4. Strong nuclear force
25
Q

Which fundamental force of nature is involved in beta-decay

A

Week nuclear force

26
Q

Equation to represent collision of two protons

A

p+p–>p+p + π^+ + π^-

27
Q

Which fundamental forces nature binds the nucleus

A

Strong nuclear force

28
Q

Which fundamental forces nature binds atoms and molecules

A

Electromagnetic force

29
Q

Which fundamental forces nature keeps the universe together

A

Gravitational force

30
Q

What happens if the colliding particles have a high energy

A

Greater variety of new particles are produced

The mass of the particles produced could be greater

31
Q

What are leptons?

A

Particles that feel the weak force and not the strong force
They appear to have no internal structure and are now considered to be elementary particle
Are point particles with no finite dimension

32
Q

What are elementary particles

A

And elementary particle is a particle that has no other particles inside it or has no subparts to it

33
Q

What are hadrons?

A

Particles that feel both are strong and weak force

They can be divided into two families the baryons and mesons

34
Q

What are baryons?

A

Baryons have masses greater than or equal to that of the proton
Baryon means ‘heavy’ in Greek
Protons, neutrons and heavier particles are baryon

35
Q

What are mesons?

A

Mesons have masses between electrons and protons

36
Q

What is anti-matter

A

Particle/matter that has the same mass as another particle with opposite charge

37
Q

Which was the first anti-matter particle discovered during the study of cosmic rays in?

A

The positron

e^+ or e with bar

38
Q

What is pair production

A

The creating of particles and antiparticles from energy

for example electron & positron

39
Q

The six quarks

A 
Up 
down 
strange 
charmed 
bottom 
top
(In order of increasing mass)
40
Q

What are mesons made up of?

A

One quark and one anti-quark

41
Q

What are baryons made up of?

A

Three quarks

42
Q

Of what do protons consists?

A

Consists of two up quarks and one down quark

43
Q

Of what do neutrons consists?

A

Consists of one up quark and two down quarks

44
Q

What happens when a particle meets its anti-particle

A

They annihilate/ pair annihilation

Matter disappears and energy is produced

45
Q

What famous Irish writer first thought up the name ‘quark’?

A

James Joyce

46
Q

Write a nuclear equations to represent the splitting of lithium nucleus by a proton.

A

7/3 Li +1/1 H—> 4/2He + 4/2He + energy

Physic (4 decks)

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