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Photoelectric effect correct answers -When light of a sufficiently high frequency (typically blue to ultraviolet light) is incident on a metal in a vacuum, the metal atoms emit electrons. -albert einsteins 1905 explanation of the photoelectric effect won him the nobel prize. -Electrons liber...

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photoelectric effect

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Solutions.
Photoelectric effect correct answers -When light of a sufficiently high frequency (typically blue
to ultraviolet light) is incident on a metal in a vacuum, the metal atoms emit electrons.

-albert einsteins 1905 explanation of the photoelectric effect won him the nobel prize.

-Electrons liberated from the metal produce a current.

-light beams of greater intensity produce larger current in this way.

-higher the intensity of the light beam, the greater the number of photons per unit time that fall
on an electrode, producing a greater number of electrons per unit time liberated from the metal.

-when the lights frequency is above the threshold frequency, the magnitude of the resulting beam
is directly proportional to the intensity (and amplitude) of the light beam

Threshold Frequency (ft) correct answers -minimum frequency of light needed to eject electrons
from a metal surface

-depends on the type of metal being exposed to radiation

-"all or nothing" response; if frequency of the incident photon is less than the threshold
frequency (f<fT), than no electron will be ejected because the photons do not have sufficient
energy to dislodge the electron from its atom.

Energy of a photon correct answers E=hf

E=energy of the photon of light
h= planck's constant (6.626 X 10^-34 J*S)
f=frequency of light

can also find wavelength of photon after this using
c=f(lamda)

maximum kinetic energy of ejected electron correct answers the difference between hƒ and hƒt

W: work function = hƒt

maximum b/c the actual kinetic energy depends on the specific subatomic interactions between
the photon and the metal atom.

-KEmax only occurs when all the energy of a photon is transferred to the ejected electron

,Work function equation correct answers the amount of energy needed to dislodge an electron
from the surface of a material

W=hft

The Photoelectric Effect correct answers The emission of electrons from a material when light of
certain frequencies shines on the surface of the material

How does the work function relate to the energy necessary to emit an electron from a metal?
correct answers -The work function describes the minimum amount of energy necessary to emit
an electron. Any additional energy from a photon will be converted to excess kinetic energy
during the photoelectric effect.

What does the threshold frequency depend upon? correct answers -Depends on the chemical
composition of the metal (that is, the identity of the metal itself)

What electrical phenomenon results from the application of the photoelectric effect. correct
answers -The accumulation of moving electrons creates a current during the photoelectric effect

i.e. solar panels

Bohr Model: light absorption and emission correct answers -Electron can be excited by a photon,
to get to an excited state, moving from the original orbit to a higher orbit.

atomic absorption correct answers Absorption of radiation by atoms. The radiation is supplied by
an external source. Atomic absorption is the atomic analog of molecular absorption
spectroscopy.

Atomic emission correct answers Energy from some external process raises atoms into a
spectroscopically excited state. The excited state atoms themselves then act as a source, re-
emitting radiation (a photon) as they decay back to the ground state.

fluorescence correct answers a material absorbs light at one wavelength and then emits light at a
longer wavelength

-if one excited a fluorescent substance, such as a rube, emerald, or phosphors found in
fluorescent lights, with ultraviolet radiation, it will being to glow with visible light.

What determines the absorption spectrum of a single atom? correct answers -The energy
differences between ground-state electrons and higher-level electron orbits determine the
frequencies of light a particular material absorbs, i.e. its absorption spectrum

True/False:
Small changes in structure only minimally impact light absorption and emission patters correct
answers False

,-Small changes, such as protonation and deprotonation, change in oxidation state and bond order,
and others may cause dramatic changes in light absorption in a material.

During which electronic transitions is photon emission most common? correct answers -When
electrons transition from a higher-energy state to a lower energy-state, they will experience
photon emission.

What causes fluorescence? correct answers -fluorescence is a special stepwise photon emission
in which an excited electron returns to its ground state through one of more intermediate excited
states.

-Each energy transition releases a photon of light. With smaller energy transitions than the initial
energy absorbed, these materials can release photons of light in the visible range.

Mass defect and energy correct answers E=mc^2
m= mass defect = mass of protons and neutrons individually- mass of the element
c=speed of light

mass defect correct answers -the difference between the mass of an atom and the sum of the
masses of its protons, neutrons, and electrons

-result of matter that has been converted to energy

nucleons correct answers protons and neutrons in the nucleus

strong nuclear force correct answers the powerful attractive force that binds protons and neutrons
together in the nucleus

four fundamental forces correct answers gravity, electromagnetic force, strong nuclear force,
weak nuclear force

binding energy correct answers the energy that holds a nucleus together, equal to the mass defect
of the nucleus.

weak nuclear force correct answers -an attractive force that acts only over a short range

-contributes to the stability of the nucleus, one millionth as strong as the strong nuclear force.

Define the terms:
Strong nuclear force
Mass Defect
Binding Energy correct answers Strong Nuclear Force:
-one of the four fundamental forces of nature and provides the adhesive force between the
nucleons (protons and neutrons) within the nucleus.

Mass Defect:

, -Apparent loss of mass when nucleons come together as some of the mass is converted into
energy

Binding energy:
-That energy is called the binding energy

how does mass defect relate to binding energy? correct answers -Mass defect is related to the
binding energy such that there is a transformation of nuclear matter to energy with a resultant
loss of matter

-related by E=mc^2

What are the four fundamental forces of nature? correct answers force of gravity
electromagnetic force
strong nuclear force
weak nuclear force

isotopic notation correct answers notation that shows the chemical symbol, atomic number, and
mass number for an isotope of an element

Atomic number (Z) correct answers the number of protons in the nucleus of an atom

Mass Number (A) correct answers the sum of the number of neutrons and protons in an atomic
nucleus

Fusion correct answers -Occurs when small nuclei combine to form a larger nucleus

Ex:
-many stars power themselves by fusing four hydrogen nuclei to make one helium nucleus,
which can produce 3.85 X 10^26 joules/second, which accounts for the mass defect that arises
from the formation of helium nuclei from hydrogen nuclei.

Hydrogen fusion in the sun, creating helium nuclei correct answers

Fission correct answers -process by which a large nucleus is split into smaller nuclei.
Spontaneous fission rarely occurs.

-through absorption of a low-energy neutron, fission can be induced in certain nuclei.

-some fission reactions release more neutrons because these other neutrons will cause a chain
reaction in which other nearby atoms can undergo fission, in turn releases more neutrons,
continuing the chain reaction.

Radioactive decay correct answers -a naturally occurring spontaneous decay of certain nuclei
accompanied by the emission of specific particles.

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