Nuclear Physics Flashcards
(43 cards)
What unexpected result did Rutherford observe in his experiment?
Some alpha particles were scattered through large angles (>90 degrees)
What hypothesis did Rutherford propose based on this observation?
Most of the mass of the atom is contained in a small, dense nucleus
How does the closest approach method work?
Put the initial kinetic energy of the alpha particle equal to the electrostatic potential energy, and solve for r
What can affect the outcome of the closest approach method?
Recoil of the target nucleus and the size of the alpha particles
What does the closest approach method provide?
An upper limit for the size of the nucleus, or in other words, how close the alpha particle needs to get in order for the SNF to cause the two particles to fuse
What pattern is produced when electrons are diffracted?
Ringed diffraction patterns
What is the relationship between the de Broglie wavelength and the nuclear radius?
When they are comparable, the nucleus acts as a circular aperture, and produces a diffraction pattern
Recall from last year that the diffraction effect is greatest when the slit width is approximately equal to wavelength
What is a limitation of the electron diffraction method?
Difficulty in estimating the position of the first minimum
How does the precision of the electron diffraction method compare to the closest approach method?
More precise due to the small wavelength of electrons
What proportionality exists between radius an nucleon number?
Radius is proportional to the cube root of the nucleon number
What is R0 in the nuclear radius equation?
Radius of a single nucleon
What are the four reasons an atomic nucleus might undergo a decay event?
- Too many protons
- Too many neutrons
- Too many nucleons in general
- Too much energy
These factors lead to instability in the nucleus, prompting decay.
What is gamma decay?
Release of a photon from an excited nucleus, returning it to the ground state.
The nucleus may not be unstable, just in an excited state.
How does the penetrating power of radiation vary?
It depends on how strongly the radiation interacts with matter.
Alpha particles are easily blocked, while gamma rays require dense materials.
True or False: Background radiation is considered safe.
True.
Life on Earth has evolved in its presence.
What law does the intensity of nuclear radiation obey?
The inverse square law.
This law states that intensity decreases with the square of the distance from the source.
What does the decay constant represent?
The probability of a given particle decaying in one second.
Its value ranges from 0 to 1.
What is the definition of activity in radioactivity?
The rate at which a sample decays, measured in decay events per second, or Becquerels.
Activity is given by A = λN.
What is the half-life of a substance?
The time taken for the initial number of undecayed particles to reduce by 50%
How does carbon dating work?
By measuring the relative abundance of C-14 to C-12 in organic material and comparing that to current C-14 levels.
This method assumes that the amount of C-14 in natrue has remained constant over time
What must happen for a stable substance to become radioactive (induced radioactivity)?
A change to the nuclear configuration must occur.
This can happen under specific circumstances, such as neutron bombardment.
What is nuclear contamination?
The unintended release of radioactive materials into the environment.
This poses health risks and often results from accidents or improper disposal.
What is the atomic mass unit equivalent to?
One twelfth the mass of a carbon-12 atom
What is binding energy?
The amount of energy required to separate all the nucleons in the nucleus
