Radiation from a star passes through a thin cloud of gas. A researcher investigates how individual atoms in the gas respond to this radiation.
The table shows the allowed energy levels of an electron in one type of atom.
| Energy level | Energy / J |
|---|---|
| 1 | 1.0 × 10⁻¹⁹ |
| 2 | 3.5 × 10⁻¹⁹ |
| 3 | 7.5 × 10⁻¹⁹ |
The radiation contains photons P and Q.
| Photon | Energy / J |
|---|---|
| P | 2.5 × 10⁻¹⁹ |
| Q | 4.0 × 10⁻¹⁹ |
Photon P reaches one atom of this type. Photon Q reaches a second atom of the same type. In each atom, the electron is at energy level 1.
Explain what happens when each photon reaches its atom.
A different atom has an electron at energy level 3. The electron moves directly from energy level 3 to energy level 1.
Explain why the emitted photon has a higher frequency than photon P or photon Q.
104 exam-style questions on Edexcel GCSE Physics 5.4 Uses and dangers of EM radiation, covering 5.4.1 Dangers of electromagnetic radiation, 5.4.2 Uses of electromagnetic radiation, 5.4.3 Radio waves and oscillations in circuits, and 5.4.4 Changes in atoms and nuclei generating radiation. Each one has a worked solution and a mark scheme showing where the marks go.