A clean metal surface is illuminated by monochromatic radiation. No photoelectrons are emitted when the frequency is below a certain value, even when the intensity is very large.

A metal has a threshold frequency of $8.1\times 10^{14}\ \text{Hz}$. Radiation of frequency $1.20\times 10^{15}\ \text{Hz}$ is incident on the metal.

Electrons are sent through a double-slit apparatus one at a time. Each electron is recorded as a small dot at a definite position on a screen. After many electrons have been recorded, alternating bright and dark bands are visible.

A proton and an electron are each accelerated from rest through the same potential difference. Non-relativistic motion may be assumed.

An X-ray photon is Compton-scattered by an electron that may be treated as initially free and at rest.

Several metal surfaces are illuminated by monochromatic sources. The observations record whether photoelectrons are emitted.

In a photoelectric experiment, the stopping potential $V_s$ is measured for different frequencies $f$ of incident light. A straight-line graph of $V_s$ against $f$ is obtained. Two points on the best-fit line are $(6.0\times 10^{14}\ \text{Hz},\ 0.40\ \text{V})$ and $(8.0\times 10^{14}\ \text{Hz},\ 1.23\ \text{V})$.

Radiation of wavelength $300\ \text{nm}$ is incident on a potassium surface. The stopping potential is $0.85\ \text{V}$.

A beam of electrons with momentum $1.5\times 10^{-23}\ \text{kg m s}^{-1}$ passes through a narrow slit of width $2.0\times 10^{-10}\ \text{m}$. A detector is moved in a circular arc around the slit to measure the electron intensity at different angles.

Electrons are accelerated from rest through a potential difference of $150\ \text{V}$ and then pass through a thin graphite film, producing diffraction rings on a screen.

An X-ray photon of wavelength $3.00\times 10^{-12}\ \text{m}$ is scattered by a free electron through an angle of $60.0^\circ$.

The spectrum of X-rays scattered from a carbon target is measured at several scattering angles. At a non-zero scattering angle, two peaks are observed in the detected intensity.

A photoelectric cell is illuminated with monochromatic light of different frequencies. For each frequency the stopping potential is measured for a clean metal cathode.

The current in a photoelectric cell is measured as the collector potential is varied. Curves are shown for two intensities at the same frequency and for a third curve at a higher frequency.

An experiment sends electrons through a double-slit apparatus one at a time. The screen is recorded after increasing numbers of detected electrons.

The table gives the momentum of three moving objects that might be directed at a crystal with atomic spacing of order $10^{-10}\ \text{m}$.

Two experiments are compared as evidence for the particle nature of light: the photoelectric effect and Compton scattering.

Compton scattering is often described as a collision between a photon and an electron, but the analogy with a collision between two solid balls is limited.

A very low-intensity ultraviolet beam and a high-intensity red beam are each incident on a zinc surface. The table summarizes the observed emission.

Electrons are accelerated from rest through a potential difference before passing through a thin graphite film. The diameter of one diffraction ring is measured for different accelerating potentials.

A beam of electrons passes through a narrow slit. A movable detector measures the intensity at different angles from the central direction.

X-rays are incident on a carbon target. The scattered spectrum is measured at a fixed scattering angle.

Compton scattering measurements are made at different photon scattering angles. The wavelength shift is plotted against $1-\cos\theta$.

A clean zinc plate is connected to a sensitive ammeter in a photoelectric cell. Very weak ultraviolet radiation causes an immediate current, but intense visible radiation causes no current.

The maximum kinetic energy $E_{\max}$ of photoelectrons emitted from a metal is measured for different frequencies $f$ of incident light. The graph is a straight line. It crosses the frequency axis at $5.0\times10^{14}\ \text{Hz}$ and has $E_{\max}=1.24\ \text{eV}$ when $f=8.0\times10^{14}\ \text{Hz}$.

An electron and a small dust grain both move in a laboratory. The electron speed is $1.5\times10^6\ \text{m s}^{-1}$. The dust grain has mass $1.0\times10^{-12}\ \text{kg}$ and speed $0.10\ \text{m s}^{-1}$.

A Compton scattering event is represented by the directions of the incident photon, the scattered photon and the recoil electron. The incident and scattered photon wavelengths are given.

Two monochromatic beams, A and B, are incident separately on the same metal cathode in a photoelectric cell. The beams have the same intensity. The current-potential curves are shown.

Electrons are accelerated from rest through a potential difference of $150\ \text{V}$ and directed at a thin crystalline film. A detector records the first minimum in electron intensity at an angle of $13^\circ$ from the incident beam direction.

Electrons are sent one at a time through a double-slit arrangement. Each electron produces one localized dot on a screen. After many electrons have arrived, a pattern of bright and dark bands is observed. A detector is then placed near the slits to determine which slit each electron passes through.

X-ray photons of wavelength $0.0710\ \text{nm}$ are incident on a carbon target. Scattered photons are detected at $90^\circ$ to the incident direction. Treat the scattering electrons as free.

An electron beam is used to investigate a regular array of atoms in a thin solid film. The effective aperture spacing is $0.20\ \text{nm}$. The electrons are accelerated from rest through $5.0\ \text{kV}$.

In a photoelectric experiment, two measurements of stopping potential are made for the same metal surface. At $f=7.0\times10^{14}\ \text{Hz}$ the stopping potential is $0.48\ \text{V}$. At $f=1.00\times10^{15}\ \text{Hz}$ the stopping potential is $1.72\ \text{V}$.

A Compton scattering experiment records the spectrum of X-rays scattered from a graphite target. At a fixed scattering angle, the spectrum contains one peak at the incident wavelength and a second peak at a longer wavelength. In another run, the wavelength shift of the second peak is $1.20\ \text{pm}$.

Gamma-ray photons of wavelength $4.00\ \text{pm}$ are Compton scattered by free electrons. Scattered photons are observed at angles of $60^\circ$ and $180^\circ$ to the incident direction.

A student claims: "The photoelectric effect proves that light is only a particle, and electron diffraction proves that electrons are only waves." An electron diffraction tube uses a crystalline target with atomic spacings of about $0.25\ \text{nm}$.