Final Exam Flashcards Physics 2

mass defect

-The mass of a nucleus is always less than the sum of the masses of the individual protons and neutrons that make up the nucleus, where energy corresponding to the mass defect is equal to the nuclear binding energy

In atomic nucleus, the nuclear force binds

neutrons and protons together

⁢delta 𝑚=

(sum of mass of protons+ sum of mass of neutrons)−mass of nucleus

Fission process

the total number of nuclei does not remain constant but the number of protons and neutrons does remain constant

in spontaneous fission reaction, the total mass of the products is ____ the mass of the original elements

less than

Heisenberg Uncertainty Principle

The uncertainty principle states that we cannot know both the position and speed of a particle,

A quark

building blocks of matter, combine to form particles like protons and neutrons, making up the nucleus of an atom

Hadrons

particles that interact through the strong force; baryons (made up of 3 quarks), mesons (1 quark and 1 antiquark)

leptons

fffundamental particle that does not feel strng nuclear force

Baryon number

Each baryon has B=+1, each antibaryon has B=−1, and non-baryons
have B=0

Conservation of Baryon Number

Experiments show that the total baryon number remains the same
before and after any process involving baryons.

Lepton Number

Each lepton is assigned a lepton number L=+1, anti-leptons L=−1,
and non-leptonic particles L=0

Conservation of Lepton number:

In any particle reaction or decay, the total lepton number before the
reaction equals the total lepton number after the reaction.

In Feynman diagrams, the electromagnetic force is

shown by the exchange of a photon, the particle that carries the electromagnetic interaction

In Feynman diagrams, the strong force is shown throughnteraction.

the exchange of gluons, the force-carrying particles of the strong interaction

The weak force is carried by the heavy W⁺, W⁻, and Z⁰ bosons.
In Feynman diagrams, weak interactions are shown t one of these bosons.

whenever
particles exchange or emit one of these bosons

Dark energy:

An unknown form of energy that
causes the universe’s expansion
to accelerate.

Dark matter:

It is a form of matter we cannot see
directly, and its properties are
different from all known particles in
the Standard Model.

Case C

fission process:

total binding energy of fragments is less than the binding energy of the original nucleus

Fusion Process:

the kinetic energy of the fusing nuclei is large enough to overcome their mutual electrostatic repulsion

Case A

Why do Hydrogen proton-proton not spontaneously fuse?

Nuclei are too far apart and are moving too slowly

Coloumb force between two protons

Case C

Nuclear Stability

determined by the binding energy per nucleon of the nucleus, which is the energy needed to separate a nucleon from the nucleus.

A nucleus with a greater binding energy per nucleon is more stable than a nucleus that has less binding energy per nucleon.

Atomic Number Z =

the number of protons in the nucleus

Electron Family

Tau Family

Le:

- e-, ve=> +1

• ve=> -1

• anything else => 0

Lt:

• T-, vt=> +1

• Anti-tau neutrino => -1

• anything else => 0

Neutron Number N =

= the number of neutrons in the nucleus

Mass Number A

= the number of neutron and proton in the nucleus

The isotopes of an element have the same _ but different _

Z value (# protons), different A and N values (sum of protons + neutrons, # of neutrons)

When electrostatic force and strong force are equal..

a stable nucleus
is created!

Nuclear Stability: Neutrons add without _

attractive force, without repulsion

Binding energy

the energy required to hold the
nucleus together, coming from the strong nuclear force

Binding Energy Formulas

Nuclear Fusion

occurs when light nuclei combine into a heavier one, releasing energy because some mass is lost in the process.

Nucelar Fission

For nuclei with A>60, the binding energy per nucleon decreases, so splitting a large nucleus into smaller ones (fission) creates
more stable nuclei.
Energy is released in fission because the fragments have far more kinetic energygy than the original neutron and nucleus.

Fission releases energy from ___ nuclei, while fusion releases energy from _____ nuclei.

large, small

For A<60:
Fusion will ____ energy.
Fission will ____ energy.

release, consume

For A>60:
Fusion will ____ energy.
Fission will ____ energy.nergy.

consume, release

Half-life is _____ proportional to the decay constant

inversely

The decay rate____

also decreases exponentially over time, meaning a radioactive sample produces fewer and fewer decays per second

Alpha decay

a type of radioactive decay in which an unstable nucleus releases an alpha particle to become more stable.

Beta decay

when a nucleus changes a neutron or proton
and emits an electron or positron.

Gamma decay

when an excited nucleus releases energy by
emitting a gamma photon

Wave-particle duality

Electrons and photons can
sometimes behave like particles
and sometimes like waves

Quantization:

certain physical properties can only
take on specific discrete values instead
of any value in between

Rydberg Formula

the wavelengths in hydrogen’s spectrum follow a simple empirical formula

Light absorbed when ___. Light is released when ____.

low energy orbit→high energy orbit

high energy orbit→low energy orbit

Bohr Model

Bohr Model Assumptions:
1. Electrons travel in fixed circular orbits.
2. Only certain stable orbits are allowed, with no energy loss.
3. Light is emitted or absorbed when electrons change orbits.
4. Each orbit’s circumference equals an integer multiple of the
electron’s de Broglie wavelength

Bohr radius

For Hydrogen, the orbit with the smallest radius (n=1)

At rest, the total energy of an electron is the sum of ___

kinetic and potential energy

____ is emitted or absorbed whenever an electron transitions between allowed energy levels in an atom

Light

Uncertainty Principle

It is physically impossible to measure simultaneously the exact position and exact linear momentum of a

particle

Quantum tunneling:

The particle has a nonzero
probability of being foun

d
outside the box.

When an electron jumps from a higher to a lower atomic orbit, the atom emits a photon with an energy 𝐸photon that equals the electron energy 𝐸𝑚 of the higher orbit minus the electron energy 𝐸𝑛 of the lower orbit, where 𝑚 and 𝑛 are positive integers with 𝑚>𝑛

𝐸photon=𝐸𝑚−𝐸𝑛

The energy of a photon 𝐸photon equals the product of Plank's constant ℎ and the speed of light 𝑐 , divided by the photon's wavelength 𝜆 .

𝐸photon=ℎ⁡𝑐/𝜆

Combine the two photon energy equations, then solve for the wavelength.

𝜆=ℎ⁡𝑐/(𝐸𝑚−𝐸𝑛)

𝜆=ℎ⁡𝑐/(𝐸𝑚−𝐸𝑛)

Because there is an inverse relationship between the emitted photon wavelength and the energy lost by the atom during the transition, the longest wavelength photon is emitted from the ____ energy transition

smallest

B4+

Wave Evidence of Light

-Double-slit interference pattern
-Diffraction through narrow slits
-Reflection and refraction in optics

Particle Evidence of Light

Blackbody radiation
Photoelectric effect
Compton Scattering

Momentum of a Photon

p = E/c = h/λ

de Broglie wave- length of a particle

λ= h/p = h/mv

Wien’s displacement law

λmax T = 0.289 × 10^-2 m · K

pPhotoelectric effect

is the emission of electrons from a
material when it is hit by light.
It takes energy from light to liberate an electron from the surface of a material

the maximum kinetic energy for these liberated photoelectrons

KEmax = hf - work function

Work function

the minimum energy with which an
electron is bound in the metal

Energy of photon

E= hf

Momentum of a photon

p= hf/c = h/ λ

Compton Scattering

photon’s collision with other
particles is similar to a collision between two billiard balls, causing change in wavelength and evidence that light exhibits particle behavior

Rank de Broglie wavelength from smallest to longest

B< A<D<C

After a collision, a photon's wavelength is always____ than its wavelength before the collision because of momentum transfer

longer

Michelson-Morley Experiment

showed that the speed of light is the same in all directions

Principle of relativity

All the laws of physics are the same in all
inertial frames

The constancy of the speed of light

the speed of light in a vacuum is constant in
all inertial frames, regardless of the source or
observer’s motion.
In relativistic mechanics there is no such thing
as absolute length or absolute time

Proper Time

the interval between two events measured by an observer for whom the events occur at the same place.

time dilation

t proper = 2d/c

Length Contraction

The length of an object measured in a reference frame that is moving with respect to the object is always less than the proper length

Lorentz Transformation

connects space and time between
moving reference frames, ensuring that the speed of light remains constant for all observers.

Momentum and energy

When the velocity is much smaller than the speed of light v≪c,
the relativistic momentum and kinetic energy reduce to their
Newtonian forms

General relativity

All the laws of nature have the
same form for observers in any
frame of reference, accelerated or
not.
In the vicinity of any given point, a
gravitational field is equivalent to
an accelerated frame of reference
without a gravitational field.

Relativistic gamma, kinetic energy, and momentum formulas

angle > angle prime