CourseCourseConceptConceptDocumentDocument

CAIE A-Level Physics A2 22.4 Energy Levels in Atoms and Line Spectra Questions

Practise explaining discrete atomic energy levels, interpreting emission and absorption spectra and calculating photon energy or frequency from level differences.

Syllabus
2028–2030
Course
Physics 9702
Level
A2

Exam points

  • explain discrete electron energy levels in isolated atoms
  • interpret emission and absorption line spectra as transitions between allowed energy levels
  • calculate photon energy or frequency from the energy difference between levels

Covered syllabus points

22.4.1—There are discrete electron energy levels in isolated atoms (e.g. atomic22.4.2—The appearance and formation of emission and absorption line spectra22.4.3—Hf = E1 – E2

Question 1

[Maximum number: 3]

Some of the electron energy bands in a solid are illustrated in Fig. 12.1.

Fig. 12.1

Fig. 12.1

In isolated atoms, electron energy levels have discrete values. Suggest why, in a solid, there are energy bands, rather than discrete energy levels.

Question 2

[Maximum number: 6]

A beam of light consists of a continuous range of wavelengths from 420 nm to 740 nm . The light passes through a cloud of cool gas, as shown in Fig. 11.1.

Fig. 11.1

Fig. 11.1

Question (a)

(a)

The spectrum of the light emerging from the cloud of cool gas is viewed using a diffraction grating.
Explain why this spectrum contains a number of dark lines.

[ 4 ]

Question (b)

(b)

Some of the electron energy levels of the atoms in the cloud of gas are represented in Fig. 11.2.

Fig. 11.2 (not to scale)

Fig. 11.2 (not to scale)

[ 2 ]

Question (i)

(i)

Use data from (i) and your answer in (i) to show, on Fig. 11.2, the changes in energy levels giving rise to the dark lines in (a).

[ 2 ]

Question 3

[Maximum number: 8]

Fig. 8.1 shows the lowest four energy levels of an electron in an isolated atom.

Fig. 8.1

Fig. 8.1

Fig. 8.2 shows the lines in the emission spectrum of the atom that correspond to the transitions of the electron from n=3 to n=1 and from n=4 to n=1.

Fig. 8.2

Fig. 8.2

Question (a)

(a)

Explain, with reference to photons, why there is a single frequency of electromagnetic radiation that corresponds to each of these transitions.

[ 2 ]

Question (b)

(b)

On Fig. 8.2, draw a line that corresponds to the transition of the electron from n=2 to n=1. Label this line A.

[ 2 ]

Question (c)

(c)

On Fig. 8.2, draw a line that corresponds to the transition of the electron from n=3 to n=2. Label this line B.

[ 2 ]

Question (d)

(d)

The frequency of radiation represented by line A is fAf_{\mathrm{A}}. The frequency of radiation represented by line B is fBf_{\mathrm{B}}. The energy of the ground state (n=1) is E1E_{1}.

Determine an expression, in terms of fA,fB,E1f_{\mathrm{A}}, f_{\mathrm{B}}, E_{1} and the Planck constant h, for the energy E3E_{3} of the energy level n=3.

E3=E_{3}=
[ 2 ]

Question 4

[Maximum number: 4]

A beam of light consists of a continuous range of wavelengths from 420 nm to 740 nm . The light passes through a cloud of cool gas, as shown in Fig. 11.1.

Fig. 11.1

Fig. 11.1

The spectrum of the light emerging from the cloud of cool gas is viewed using a diffraction grating.
Explain why this spectrum contains a number of dark lines.

All question bank results loaded