Physics #9 Flashcards
photoelectric effect
when light with sufficiently high frequency is incident on a metal in a vacuum, the metal atoms emit electrons
what do ions released by the photoelectric effect product?
current
when the light’s frequency is above the threshold frequency, the magnitude of the resulting current is directly proportional to _____
the intensity (and amplitude) of the light beam
threshold frequency
the minimum frequency of light that causes ejection of electrons
why is the photoelectric effect an all or nothing response
if the frequency of the incident photon is less than the threshold frequency, then no electron will be ejected because the photons do not have sufficient energy to dislodge the electron from its atom
when is the maximum kinetic energy of an ejected electron achieved?
when all possible energy from the photon is transferred to the ejected electron.
in the photoelectric effect, is the speed of ejected electrons dependent on the frequency of light or its intensity?
frequency
the number of electrons ejected depends on intensity
Borh model of atom
electron energy levels are stable and discrete, corresponding to specific orbits
IR spectroscopy
determine chemical structure because different bonds will absorb different wavelengths
we see the colors that are ___ absorbed
not
T/F: small changes in chemical structure minimally impact light absorption and emission patterns
false
just protonating a structure can make a huge difference in absorptions patterns (phenylthaline)
how does fluorescence occur?
fluorescent substance excited with ultraviolet radiation and then the electrons step-wise fall back down which releases lower energy photons in the visible range.
the mass of every nucleus is ______ than the mass of protons and neutrons combines
smaller
mass defect
the mass of every nucleus is smaller than the mass of protons and neutrons combines
the result of matter that has been converted to energy.
strong nuclear force
the attraction between the protons and neutrons in the nucleus which overcomes the repulsive electromagnetic force between the protons
releases energy which is the mass defect
what size nuclei are the most stable?
intermediate size
what are the 4 fundamental forces of nature?
strong nuclear force
weak nuclear force
electrostatic forces
gravitation
fusion
when small nuclei combine to form a larger nucleus
fission
a process by which a large nucleus splits into smaller nuclei
does spontaneous fission occur a lot?
no
radioactive decay
a naturally occurring spontaneous decay of certain nuclei accompanied by the emission of specific particles
discuss alpha particles and lead sheets
alpha particles interact with matter very easily, hence they do not penetrate shielding such as lead sheets
do alpha particles carry any charge?
yes, +2 because they have 2 protons and do not carry any electrons
where does the electron come from for beta decay?
electrons do not reside in the nucleus, but they are emitted by the nucleus when a neutron decays into a proton, a beta particle, and a antineutrino
is beta particle or alpha particle more penetrating?
beta particle
what does positron decay release?
neutrino and positron
what do gamma rays do?
high-energy, high-frequency photons. They carry no charge and simply lower the energy of the parent nucleus without changing the mass number or the atomic number
do gamma rays have a charge?
no
electron capture
unstable radionuclides are capable of capturing an inner electron that combines with a proton to form a neutron, while releasing a neutrino.
half-life
the time it takes for half of a radioactive sample to decay
how many nuclei are there per mole of a sample
avogadro’s: 6.022 x 10^23
does nuclear fusion or nuclear fission release energy?
both
does positron or beta decay release antineutrino?
beta decay
beta-negative decay and beta-positive decay are the correct terms
nice
what type of nuclear decay can be detected in an atomic absorption spectrum?
gamma: releases electromagnetic radiation rather than nuclear fragments.
compare fusion and fission
fusion: combining
fission: breaking down
T/F: for an electron to jump to a higher energy level it has to absorb the exact frequency of energy that puts it there
True
why is energy released in both nuclear fusion and fission?
the nuclei that are formed are more stable (energy was released)
an alpha particle is a ____ nucleus
helium
to jump energy levels, need ______ amount of energy absorbed
exact
all light travels at ______
speed of light
