Physics 110
Physical Science
Name _______________
Date ________________
Exercise 12: Atomic Physics
Check dimensions and proper significant figures.
Planck’s constant h = 6.626x10−34 J–s
e = 1.6x10−19 coulombs (C)
Quantized Charge
1. An object has a net charge q of −3.2x10–13 coulombs. How many more electrons are
there than protons (q = Ne)?
Quantized Light
2. A green laser pointer emits photons of frequency 5.64x1014 Hz. What is the energy of
one photon (Eonephoton) associated with the laser?
Hydrogen atom
Bohr radius r1 = 0.053 nanometers (nm)
Hydrogen ground state E1 = −13.60 electron volts (eV)
3. What is the radius of the electron orbit for a hydrogen atom for n = 3?
The various Bohr energy levels for the electrons in the hydrogen atom are
E1 = −13.6 eV
E2 = E1/4 = −3.40 eV
E3 = E1/9 = −1.51 eV
If an electron jumps from the n = 3 to n = 2 level,
a. Is it absorbing or emitting a photon?
b. What is the change in energy (in eV)?
c. Use the conversion factor 1 eV = 1.6x10−19 J to calculate the energy change in joules.
d. Using Planck’s constant h, calculate the frequency of the photon.
a) 4.6x1014 Hz b) 6.2x1013 Hz c 7.3x1013 Hz d. None of the above.
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