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### Quantum Physics Sample Problems

1. The threshold frequency of sodium is 5.6 x 1014 Hz. It is irradiated with light of 8.6 x 1014Hz frequency. What is the energy of the ejected photoelectrons is J and in eV?
2. The stopping potential of a photocell is 3.2 V. Calculate its energy in J.
3. 240 nm light is used to irradiate zinc. Its threshold wavelength is 310 nm. What is the energy of the ejected photoelectrons?
4. The work function for cesium is 1.96 eV. It is irradiated by 425 nm light. What is the energy of the ejected photoelectrons in eV? What is the speed of the ejected photoelectrons if the mass of an electron is 9.11 x 10-31 kg?
5. A 7 kg bowling ball rolls down an alley with a speed of 8.5 m/s. What is its deBroglie wavelength?
6. An electron (mass = 9.11 x 10-31kg) is accelerated by 150 V. Find the speed of the electron. What is its deBroglie wavelength?
7. Repeat for an electron accelerated by 250 V.
8. For the hydrogen atom, find the energy of the first and second energy levels. What energy is given off by a photon dropping from the second to the first level?
9. Calculate the frequency of this photon. Calculate its wavelength.