Atomic and Nuclear Phenomena Flashcards
the photoelectric effect
the ejection of an electron from the surface of a metal in response to light, normally high frequency light
current
net charge flow per unit time
threshold frequency f(t)
the minimum light frequency necessary to eject an electron from a given metal; depends on the type of metal being exposed to the radiation
energy of a photon of light
E=hf
E=energy of the photon of light
h=Planck’s constant (6.626 x 10^-34 J s)
f= is the frequency of the light
maximum kinetic energy of an electron in the photoelectric effect
Kmax=hf-W
W=work function of the metal in question
work function
the minimum energy required to eject an electron and is related to threshold frequency of that metal
W=h(f(t))
f(t)= threshold frequency
fluorescence
occurs when a species absorbs high-frequency light and then returns to its ground state in multiple steps; each step has less energy than the absorbed light and is within the visible range of the electromagnetic spectrum
mass defect
the difference between the mass of the unbounded nucleons and the mass of the bonded nucleons within the nucleus; the amount of mass converted to energy during nuclear fusion
mass defect and energy
E=mc^2
E=energy
m=mass contributed by the binding energy of the nucleus
c=speed of light
nucleons
protons and neutrons
what is the most stable kind of nucleus?
intermediate in size are the most stable (Iron), in comparison to small or large nuclei
binding energy
the energy that originated from mass defect, the energy released from protons and neutrons bind together
fusion
occurs when small nuclei combine into larger nuclei
fission
occurs when a large nucleus splits into smaller nuclei
why is energy released in fission and fusion
the nuclei formed in both processes are more stable then the starting nuclei
radioactive decay
the loss of small particles from the nucleus
alpha decay
the emission of an alpha particle which is a helium nucleus, has zero electrons, 2 protons and 2 neutrons; carries double the charge of a beta particle and is much bigger; does not penetrate shielding
beta-negative decay
the decay of a neutron into a proton, with emission of an electron and an antineutrino; more penetrating then alpha particles
beta-positive decay
also called positron emission, the decay of a proton into a neutron, with emission of a positron (a particle with the size of an electron but with a positive charge) and a neutrino; more penetrating then alpha particles
Gamma decay
the emission of a gamma ray, which converts a high-energy nucleus into a more stable nucleus
electron capture
the absorption of an electron from the inner shell that combines with a proton in the nucleus to form a neutron
half-life (T 1/2)
the amount of time required for half of a sample of radioactive nuclei to decay
exponential decay
the rate at which radioactive nuclei decay is proportional to the number of nuclei that remain
n= (no)e^-(lambda)t
no= the number of undecayed nuclei at time t=0
rate of nuclear decay
delta n/ delta t= -lambda(n)
n=number of radioactive nuclei that have not yet decayed in a sample
lambda= decay constant
decay constant (lambda)
lambda= ln2/T-half= 0.693/T-half
