Modern Physics - Energy Levels and Photoelectric Effect

Which of the following phenomena involving light can be explained with a particle model? Select two answers.

• Spectral lines

• The photoelectric effect

• Diffraction

• Thin-film interference

The figure above shows part of the energy level diagram for a hypothetical atom. Which of the transitions indicated produces the most energetic photons?

• A

• B

• C

• D

• E

A hypothetical hydrogen-like atom has energy states as represented in the energy-level diagram above. The atom is in the ground state when it absorbs a photon with frequency 2.18 x 10¹⁵ Hz . What energy state will the atom be in after it absorbs the photon?

• n = 2

• n = 3

• n = 4

• n = ∞

The ground state of a certain type of atom has energy -E₀ . What is the wavelength of a photon with enough energy to ionize an atom in the ground state and give the ejected electron a kinetic energy of 2E₀?

• 2hc/E₀

• hc/3E₀

• hc/2E₀

• hc/E₀

The graph above shows the wave function Ψ(x) of a particle moving in the region 0 < x < 4 m. At which of the following positions is the probability of finding the particle greatest?

• 2.0 m

• 4.0 m

• 2.5 m

• 0.7 m

The figure above shows graphical representations of the wave functions of two particles, X and Y, that are moving in the positive x-direction. The maximum amplitude of particle X’s wave function is A₀. Which particle has a greater probability of being located at position x₀ at this instant, and why?

• Particle Y, because the wave function of particle Y is narrower than the wave function of particle X

• Particle X, because the wave function of particle X has a longer wavelength than the wave function of particle Y

• Particle X, because the wave function of particle X spends more time passing through x₀ than the wave function of particle Y

• Particle Y, because the wave function of particle Y has a greater amplitude near x₀ than the wave function of particle X

The next two questions pertain to the following:

An electron and a positron, each of mass 9.1 x 10^-31 kilogram, are in the same general vicinity and have very small initial speeds. They then annihilate each other, producing two photons. What is the approximate energy of each emerging photon?

• 0.51 MeV

• 2.0 MeV

• 4.0 MeV

• 6.6 MeV

• It cannot be determined unless the frequency of the photon is known.

In an experiment, light of a particular wavelength is incident on a metal surface, and electrons are emitted from the surface as a result. To produce more electrons per unit time but with less kinetic energy per electron, the experimenter should do which of the following?

• Increase the intensity and decrease the wavelength of the light.

• Increase the intensity and the wavelength of the light.

• Decrease the intensity and the wavelength of the light.

• Decrease the intensity and increase the wavelength of the light.

• None of the above would produce the desired result.

The work function for a metal is . What is the threshold frequency of incident light required for the emission of photoelectrons from a cathode made of that metal?

• φ/h

• h/φ

• hφ

• φ/hc

• hc/φ

Which graph best shows the maximum kinetic energy K of the photoelectrons as a function of the frequency of incident light?

• 
• 
• 
• 
•