Physics Subject Test - ALL

What is the mass of an *electron* in atomic mass units (amu)?

0. (This doesn't mean that electrons have zero mass! Just that, compared to protons and neutrons, electrons have negligible mass.)

What is the mass of a *neutron* in atomic mas units (amu)?

1.

What is the mass of a *proton* in atomic mass units (amu)?

1.

What are the 3 main types of *radioactive decay*?

1. alpha decay 2. beta decay (and positron emission) 3. gamma decay Sometimes positron emission is categorized as its own thing.

All particles can be divided into which 2 categories?

1. fermions (purple & green) 2. bosons (red)

What are the 4 *fundamental forces* (fundamental interactions) in nature?

1. gravity 2. strong (nuclear) force 3. weak (nuclear) force 4. electromagnetism

How would the fundamental forces be arranged from weakest to strongest?

1. gravity 2. weak force 3. electromagnetism 4. strong force

What are 4 properties of particles that are relevant to how they interact with each other?

1. mass 2. charge (electric charge) 3. color (color charge) 4. spin

What are the *elementary bosons* that have been observed?

1. photons 2. gluons 3. W bosons 4. Z bosons (gravitons have not been observed)

What are the 2 types of *elementary fermions* (matter particles)?

1. quarks (purple) 2. leptons (green)

What is a *boson*?

A "force carrier" particle (plays important role in fundamental forces). It has an integer spin (1, 2, 3, etc). It does not follow the exclusion principle (bosons with the same properties can be grouped together).

What is a *fermion*?

A "matter" particle (makes up matter). It has a half-integer spin (1/2, 3/2, etc). It follows the exclusion principle (fermions with the same properties can't be grouped together).

A *photon* is which kind of elementary particle?

A boson (force carrier) with zero mass.

What is a *neutrino*?

A fermion (lepton) particle with no charge (neutral) and almost no mass. Aka, the "ghost particle" because it's almost nothing. There are lots of them in the universe, but they're very hard to detect.

A *neutrino* is which kind of elementary particle?

A fermion (matter particle), specifically a lepton.

An *electron* is which kind of elementary particle?

A fermion (matter particle), specifically a lepton.

What is a *positron*?

A positive electron: same mass but a positive charge. An electron-positron pair is an example of a particle-antiparticle pair.

What is an *electron*?

A subatomic particle that is negatively charged.

What is a *neutron*?

A subatomic particle that is neutrally charged.

What is a *proton*?

A subatomic particle that is positively charged.

What is the *electroweak force*?

A unification of electromagnetism and the weak force. These are 2 versions of the same force.

What is an *antiparticle*?

An antimatter particle. A particle that has the same mass but the opposite charge of its partner "matter" particle.

What is an *isotope*?

An atom that has the same number of protons but a different number of neutrons.

What is an *atomic mass unit* (u)?

An easy-to-use unit for measuring very small masses, like those on an atomic scale.

What makes an element *radioactive*?

An unstable nucleus that breaks down and emits particles and energy as a result.

What is a *tau*?

An unstable, charged lepton particle that is about 3000x more massive than an electron.

What is a *muon*?

An unstable, charged lepton particle that is more than 200x more massive than an electron.

What is *matter*?

Anything that has mass and volume. Almost everything we observe in the universe is made of matter. In particle physics, it's more complicated, but this definition is good enough for now.

Why are elements with high atomic numbers (above 83) radioactive (spontaneously decay)?

As the number of protons increases, there is a tipping point at which the additional strong nuclear force that comes from adding more neutrons isn't enough to balance the repulsive force that protons exert on each other. This is mostly because the strong nuclear force has such a short range.

What is an alternate symbol for a *proton*?

Because the (common) hydrogen atom has 1 proton.

Why does the number of neutrons need to be greater than or equal to the number of protons in order to have a stable nucleus?

Because the strong nuclear force that attracts protons and neutrons to each other has a much shorter range than the repulsive force that the protons experience. Protons are repelled by all of the other protons in the nucleus because they're like charges. Compared to this repulsive force, the strong nuclear force has a very short range - it only attracts things that are next to each other. So as the number of protons increases, the number of neutrons needs to increase even more to make up for the short range of the strong nuclear force.

Why are *neutrinos* so hard to detect?

Because they're super tiny, travel near the speed of light, and hardly interact with anything.

How do fermions (matter particles) exchange energy with each other?

By exchanging bosons (force-carrier particles).

How do *color charged* particles interact with each other?

By exchanging gluons in strong interactions.

How do *electrically charged* particles interact with each other?

By exchanging photons in electromagnetic interactions.

Which property does the *strong force* act upon?

Color charge.

*Einstein's famous formula*

E = mc²

Which property does the *electromagnetic force* act upon?

Electric charge.

Which fundamental force is primarily responsible for atoms bonding to form molecules?

Electromagnetic force. The positive parts of atoms (protons) are attracted to negative parts (electrons) of neighboring atoms.

Friction is caused by which fundamental interaction?

Electromagnetism.

Which leptons are the most stable?

Electrons and the 3 kinds of neutrinos.

Which subatomic particle determines the *ion* of an element?

Electrons.

Which subatomic particle has the *least mass*?

Electrons. (A proton is about 1800X more massive than an electron.)

What is *antimatter*?

Every matter particle has a corresponding antimatter particle. Antimatter is like matter's equal and opposite partner that completes the pair.

What are *leptons*?

Fermion particles that do not have color, do exist on their own, and interact primarily via the electroweak force (electromagnetism and the weak force).

What are *quarks*?

Fermion particles that have color, do not exist on their own, and interact primarily via the strong force.

A *neutron* is made of which elementary particle?

Fermions (matter particle), specifically quarks.

A *proton* is made of which elementary particle?

Fermions (matter particle), specifically quarks.

Given the mass number and the atomic number, how do you calculate the number of neutrons?

Find the difference. # neutrons = mass number − atomic number

Where does *nuclear binding energy* come from?

From the mass of protons and neutrons. Protons and neutrons give up a little bit of their mass when they form a nucleus. This little bit of mass is converted into the binding energy that holds the nucleus together.

Which boson carries the *strong force*?

Gluon.

Which boson (hypothetically) carries *gravity*?

Graviton (but it hasn't been discovered yet).

Which fundamental force is the *weakest*?

Gravity (gravitational force).

Which fundamental forces have an *infinite range*?

Gravity and electromagnetism.

Which fundamental interactions act on neutrinos?

Gravity and the weak force.

Planetary orbits are caused by which fundamental interaction?

Gravity.

Which fundamental force is not yet explained by The Standard Model?

Gravity. The gravity force carrier particle (graviton) is predicted but has not been found.

Which property does the *weak force* act upon?

Handedness and weak isospin. The weak force only acts on left-handed particles and right-handed antiparticles.

What is the significance of *E = mc²*?

It says that mass and energy can be converted into one another.

How is a boson's mass related to the range of the force it carries?

Long range forces have low mass carriers (bosons). ex: Photons are massless and carry the long-range electromagnetic force. Gluons are high mass and carry the short-range strong force.

Which property does the *gravitational force* act upon?

Mass.

Which is more abundant in the universe: matter or antimatter?

Matter. Antimatter is hardly observed in the natural universe. More commonly, antimatter is made artificially in particle accelerators, and even then, the antiparticles that are produced don't last long.

How is binding energy related to the stability of a nucleus?

More stable nuclei have higher binding energies - it requires more energy to break apart stable nuclei.

How are neutrinos different from their lepton partners (electron/electron neutrino, etc.)?

Neutrinos are neutral and have almost no mass, whereas their partners are charged and have a sizable mass.

Which subatomic particle determines the *isotope* of an element?

Neutrons.

Can *quarks* exist on their own?

No. Quarks only exist in groups and make up composite particles. Quarks combine with each other to form colorless (color neutral, "white") particles.

An *electron* is made of which elementary particle?

None (as far as we know). Electrons are elementary particles themselves.

Where does the *strong nuclear force* come from?

Nuclear binding energy.

What are the types of *electrical charge*?

Positive (+) and negative (-). The same amount of positive and negative charge add up to a neutral (0) charge.

Which boson carries the *electromagnetic force*?

Photon.

Which bosons are massless?

Photons. (And theoretically gravitons, which haven't been discovered yet.)

Which subatomic particles make up the nucleus?

Protons and/or neutrons.

Which subatomic particle determines the *identity* of an element?

Protons.

Which elementary particle has the "flavors" *up*, *down*, *strange*, *charmed*, *top*, and *bottom*?

Quarks. Quarks have quirky "flavors". Each flavor refers to a particular set of values for electric charge, spin, etc.

How is the ratio of protons to neutrons related to the stability of a nucleus?

Ratios that are closer to 1:1 are more stable. There needs to be at least as many neutrons as protons for a stable nucleus.

Which fundamental forces have a *very short range* (work only on subatomic particles)?

Strong force and weak force.

Which fundamental force is responsible for holding atomic nuclei together?

Strong force.

Which fundamental force is the *strongest*?

Strong force.

Nuclear bonding is caused by which fundamental interaction?

Strong interactions.

How does particle physics explain the fact that 2 objects can affect one another without touching?

The "invisible" force could be an exchange of force carrier particles (bosons).

How do protons stay together in the nucleus if like charges repel? Why don't they fly apart?

The *strong nuclear force* holds the protons together. It's stronger than the repulsive force that protons feel from being like charges.

What is the *weak force*?

The force responsible for radioactive decay and nuclear fusion. It changes the flavor of quarks.

What is the *strong force*?

The force that holds the nucleus together and is responsible for making protons and neutrons.

What is a *nucleus*?

The central, dense part of an atom that contains most of the mass.

What is *The Standard Model*?

The currently accepted explanation for how the building blocks of matter interact with each other via the fundamental forces. All matter is made of fundamental matter particles and all matter interactions are exchanges of force carrier particles.

At a fundamental level, what is a *force*?

The effect when force carrier particles (bosons) interact with matter particles (fermions).

What happens to the nuclear binding energy when a nucleus is split?

The energy is released as heat.

What is an *electron*?

The most stable, least massive, charged lepton particle.

What is the *mass number* (A)?

The number of protons and neutrons in an atom. (Electrons don't count because they have so little mass compared to protons and neutrons.)

What is the *atomic number* (Z)?

The number of protons in an atom.

All stable matter appears to be made of which fermions (matter particles)?

The smallest quarks and leptons: 1. the least-massive quarks (up & down) 2. the least-massive charged lepton (electron) 3. the almost massless neutrinos

What happens when a particle and its antiparticle collide?

They will disappear (destroy each other) and produce electromagnetic energy in the form of gamma rays.

How are the mass number and the atomic number represented in chemical symbol form?

Top = mass number (protons + neutrons) Bottom = atomic number (protons)

Which boson carries the *weak force*?

W and Z bosons.

Which fundamental force is responsible for nuclear decay, reactions in stars, and lepton reactions?

Weak force.

Can *leptons* exist on their own (be isolated)?

Yes.

Can protons, electrons, and neutrons be broken down into even smaller particles?

Yes.