Name ______________
AP PHYSICS
Pd ______
WS on Modern and Atomic Physics
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235
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1. Consider the alpha decay of U 92
a) What is the daughter nucleus?
b) If the masses of the particles are Uranium 235.043 u. Alpha is 4.0015 u. Daughter nucleus is
231.02 u.
i) What amount of energy is generated from a single decomposition of a Uranium atom?
ii) Assuming the Uranium atom cannot move, what will be the speed of the alpha particle?
c) If the reaction has a half-life of 1.35 million years, what percentage of uranium will remain in a
sample that is 12 million years old?
d) The daughter atom then undergoes a beta decay, what is the new granddaughter atom?
2. a) A 725 nm photon strikes a piece of metal and ejects a photoelectron at 3.12 E3 m/s.
i) What was the energy of the photon?
ii) What is the work function of the metal?
iii) What is the minimum frequency required to cause the photoelectric effect.
b) Another photon strikes the metal with a frequency of 6.13 E12 Hz.
i) Is a photoelectron ejected? Justify mathematically.
ii) If it is ejected, what is its speed?
Name ______________
AP PHYSICS
Pd ______
3. For a certain atom the energy of an electron is given by the equation
Z2 
E  R 2  where R is a constant of 13.6 eV, Z is the atomic number, and n is the energy level.
n 
Consider an atom with a Z of 4.
a) What are the energies of level 1,2,3,4?
b) What frequency photon would be required to make an electron move from level 1 to level 3?
c)
i) What is the wavelength of a photon emitted when the electron drops from level 4 to level 2?
ii) If that photon struck an alpha particle causing it to move, what would be the velocity of the alpha
particle (4.0015 u) ?
iii) What would be the deBroglie wavelength of the alpha particle?