Figure 28.20 shows another energy level diagram. In this case, energy is given in electronvolts (eV). The list shows the energies of some photons: $6.0 \mathrm{eV}, 9.0 \mathrm{eV}, 11 \mathrm{eV}, 20 \mathrm{eV}, 25 \mathrm{eV}, 34 \mathrm{eV}, 45 \mathrm{eV}$. State and explain which of these photons will be absorbed by the electrons.

An energy level diagram.

The line spectrum for a particular type of atom is found to include the following wavelengths: $83 \mathrm{nm}, 50 \mathrm{nm}, 25 \mathrm{nm}$. Calculate the corresponding photon energies in eV.

The line spectrum for a particular type of atom is found to include the following wavelengths: 83 nm 50 nm 25 nm.

(b) Sketch the energy levels that could give rise to these photons. On the diagram, indicate the corresponding electron transitions responsible for these three spectral lines.

X-rays are used to find out about the spacings of atomic planes in crystalline materials. Describe how beams of electrons could be used for the same purpose.

X-rays are used to find out about the spacings of atomic planes in crystalline materials. How might electron diffraction be used to identify a sample of a metal?

A beam of electrons is accelerated from rest through a p.d. of $1.0\mathrm{kV}$. What is the energy (in eV) of each electron in the beam?

A beam of electrons is accelerated from rest through a p.d. of $1.0\mathrm{kV}$.

Calculate the speed, and hence the momentum $\left(\mathrm{mv}\right)$, of each electron.

A beam of electrons is accelerated from rest through a p.d. of $1.0\mathrm{kV}$.

(c) Calculate the de Broglie wavelength of each electron.

A beam of electrons is accelerated from rest through a p.d. of $1.0\mathrm{kV}$. Would you expect the beam to be significantly diffracted by a metal film in which the atoms are separated by a Spacing of $0.25\times {10}^{-9}\mathrm{m}$.