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IB Physics
27.2 Group Quiz
Closest Approach: Ek = 1/2mv2 Q = 2e, q = Ze 1 fm = 10-15 m
1. An alpha particle (m = 6.64x10−27 kg) going 5.36x107 m/s will get how close to a lead (Z = 82) nucleus if it hits head on? (3.97 fm)
2. A speeding alpha particle (m = 6.64x10−27 kg) hits a cobalt (Z = 27) nucleus head on. If it comes within 56.0 fm of the nucleus’ center, how fast was it going to start with? (8.19x106 m/s)
3. A 36.0 MeV alpha particle (m = 6.64x10−27 kg) can get how close to a gold nucleus (Z = 79)? (36.0 MeV is the KE)
(6.32 fm)
Bohr Atom: and
4. What is the wavelength of the photon associated with an electron transition from n = 2 to n = 1 in a hydrogen atom? Is the photon being absorbed, or emitted? (122 nm – emitted)
5. What is the wavelength of the photon associated with an electron transition from n = 2 to n = 5 in a hydrogen atom? Is the photon being absorbed, or emitted? (434 nm – absorbed)
Nuclear Radius: Ro = 1.2 x 10-15 m (1.2 fm)
6. What is the radius of Cl-36 nucleus? (3.96 fm)
7. What is the likely mass number of a nucleus with a radius of 7.064x10-15 m? (204)
Heisenberg Indeterminacy: or
8. To effect an alpha decay, an alpha particle must “borrow” 23.0 MeV of energy. What time does it have to escape? (1.43x10-23 s)
9. A proton has an uncertainty in its velocity of ±1.20x106 m/s. What is the minimum uncertainty in its position? (13.1 fm)
Conceptual Questions:
I: How was Rutherford's atomic model different from Thomson's "plum pudding" model?
I: How did Rutherford discover the nucleus? What size did he determine for the atom and the nucleus?
I1: How does the density of a nucleus change with mass number? What is the density of the Uranium-235 nucleus? What is the density of the carbon-12 nucleus? Calculate both densities: (2.3x1017 kg m-3)
m = A(1.661x10-27 kg), V = 4/3πr3, ρ = m/V
K: Specifically what phenomenon, what observed behavior of atoms was Bohr trying to explain with his quantum atomic model?
N: Energy indeterminacy accounts for nuclear decay - particles in the nucleus "borrow" energy to escape - Where does the energy come from that they "borrow", and where does it go after it has escaped?
O: What was the Einstein-Bohr debate about? What did Einstein object to in quantum mechanics?
Particle Physics:
Part A:
Part B:
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