Particles and Waves Notes

Physics HS/Science Unit: 13 Lesson: 01 Particles and Waves Notes

The questions below can be answered by viewing the Annenburg video, Particles and Waves, or during a classroom discussion following the viewing of the film.

1. The film opens with the statement, “In the beginning, there was ______and later the ______bulb.”

2. The color at which a body glows depends upon its ______.

3. The idea that light is emitted or absorbed in discrete bundles of energy is attributed to Max ______. The constant in his equation E = h f is called ______constant.

4. What causes the charged electroscope to discharge? It is a beam of ______light.

5. The discharging of the electroscope is called by the name of the ______effect.

6. Albert Einstein won the Nobel Prize for an explanation of the ______effect.

7. In Einstein’s photoelectric effect equation: K = h f – φ, K is the ______of the electron. (work function, kinetic energy, or frequency)

8. The same man verified the photoelectric effect that measured the charge on an electron; his last name was ______. (Millikan, Fermi, Einstein, or Planck)

9. Louis de Broglie proposed that electrons (particles) might also be ______.

10.The Bohr orbits are ______because the circumferences of the orbits are standing waves – whole numbers of wavelengths of the electron. (quantized or circular)

11.Schrödinger devised a description of matter, called wave mechanics, where he made wave packets by combining waves of slightly different ______to make a wave pulse. (amplitude, frequencies, or phase)

12.Heisenberg indicated the better you know the momentum (wavelength) of an electron, the less you know about its location or momentum. This is called the ______principle. (logic, uncertainty, wave, or physics)

13.Planck and ______did not accept the quantum theory completely.

1. The hydrogen atom orbits are determined by the condition (according to de Broglie wave theory) that the electron wave is a standing wave. Standing circular waves are shown in the figure.

2. The de Broglie equation is λ = h/p, where p is the momentum of the particle, λ is the wavelength, and h is Planck’s constant.

3. Schrödinger was able to describe matter waves using Fourier synthesis techniques, creating wave packets with a small spread of frequencies (momentums).

4. Heisenberg summarized a property of the wave packet indicating that the position and momentum of a particle could not be precisely known. Δx Δp ≥ ħ/2 • Δx is the uncertainty (error) in location. • Δp is the uncertainty (error) in momentum.

The standard interpretation of this equation is that the uncertainty is not a result of not being able to make measurements sufficiently precise but rather a property of nature. Nature does not allow for both position and momentum to both be known precisely. The value of ħ is sufficiently small that this principle does not limit macroscopic measurements. It is a philosophical statement that is not universally appreciated.