The Photoelectric Effect & Atomic Spectra (Edexcel International A Level (IAL) Physics): Structured Questions

Astronomers analyse the light from a hot star. Light from the star's hot interior passes through the cooler gases in its outer atmosphere.

The spectrum of the light contains a number of dark lines, each at a specific wavelength.

Explain how the dark lines in the spectrum arise.

The diagram shows some of the energy levels in a helium atom.

One dark line in the star's spectrum is at a wavelength of 588 nm. Helium is present in the outer atmosphere of the star.

Deduce which electron transition produces this dark line.

After an atom of hydrogen has been exposed to suitable electromagnetic radiation, the atom can emit visible light. The emitted light contains a small number of different wavelengths of visible light.

Explain the process that results in the emission of different wavelengths of visible light. Your answer should include reference to energy levels in atoms.

It is also possible to make the atoms in a sample of air emit visible light.

Explain why the light emitted by the air has a large number of different wavelengths.

A photographic light meter measures the brightness of light using a photocell. Light entering the meter strikes a caesium surface inside the photocell, releasing photoelectrons, and the meter measures the current produced.

State what is meant by the work function of a metal.

Explain how observations of the photoelectric effect provide evidence for the particle nature of electromagnetic radiation.

Light of wavelength 450 nm enters the meter.

Calculate the maximum kinetic energy of the photoelectrons released from the caesium surface.

work function of caesium $=1.9\text{ eV}$

A student used two sources, A and B, of electromagnetic radiation to investigate the photoelectric effect. Radiation from A has a photon energy of 2.0 eV.

The radiation from B has a wavelength of 280 nm.

Show that this radiation has a photon energy of about 4.4 eV.

The student used the two sources of radiation to investigate the photoelectric effect for two different metals, copper and zinc.

The following statements were made by the student.

Explain the conclusions that can be made from these statements.

In the early 20th century, observations of the photoelectric effect demonstrated that light behaves as a particle.

Explain how observations from the photoelectric effect demonstrate the particle nature of light.

The diagram shows a photocell used by a student to investigate the photoelectric effect.

The student directs a beam of monochromatic light onto the metal plate.

Explain why the beam produces photoelectrons with a range of kinetic energies.

The student connected the photocell to an ammeter and a battery of negligible internal resistance, as shown.

The student varied the frequency of the light and made the following observations:

• When visible light was incident on the photocell, there was no reading on the ammeter

• When ultraviolet light was incident on the photocell, there was a reading on the ammeter

Explain why these observations are not consistent with the wave theory of light.

The student then reversed the connections to the battery.

When photoelectrons have enough kinetic energy to overcome the potential difference across the photocell, there is a reading on the ammeter.

Deduce whether there is a reading on the ammeter when ultraviolet light of wavelength $350\text{ nm}$ is incident on the photocell.

work function of metal plate in photocell = $2.3\text{ eV}$

The diagram shows some energy levels of a hydrogen atom.

State what is meant by the ground state of a hydrogen atom.

The spectrum of light from a star includes an absorption line at a wavelength of 490 nm.

Deduce the transition involved in the formation of the line with this wavelength.

Transition: .................. $\text{eV}$ to .................. $\text{eV}$

The spectrum of a star shows a set of dark lines. These dark lines can be used to identify elements present in the atmosphere of the star.

Explain how dark lines corresponding to different elements appear on this spectrum.