Energy levels and line spectraAQA A-Level Physics: Flashcards
What these 12 flashcards ask
- What is a line spectrum?
- What is a continuous spectrum?
- What do line spectra provide evidence for?
- State the equation for the photon emitted in a transition.
- Give the wavelength of the photon in terms of the two levels.
- Why are atomic energy levels negative?
- What is the ground state?
- Which transition gives a photon of shorter wavelength: a larger or smaller energy gap?
- How do you convert an energy level in eV to joules?
- What is the energy of the photon in the n = 3 to n = 2 transition of hydrogen?
- Why does each element have its own line spectrum?
- How are atoms in a discharge lamp excited?
Exam questions on Energy levels and line spectra
- A neon sign glows when a current passes through low-pressure neon gas. When its light is viewed through a diffraction grating, a few bright coloured lines are seen against a dark background instead of a continuous band of colours.Explain why the spectrum is made of separate lines and not a continuous band.2 marks
- Some of the energy levels of a hydrogen atom are: n = 1 at −2.18 × 10⁻¹⁸ J, n = 2 at −5.45 × 10⁻¹⁹ J and n = 3 at −2.42 × 10⁻¹⁹ J.A photon of energy 1.0 × 10⁻¹⁸ J passes through hydrogen gas with all the atoms in the ground state, and is not absorbed. Explain why.2 marks
- Astronomers study the light from a cloud of hydrogen gas. Some of the energy levels of a hydrogen atom are: n = 1 at −13.6 eV, n = 2 at −3.40 eV, n = 3 at −1.51 eV and n = 4 at −0.85 eV.Calculate the wavelength of the photon emitted when an electron falls from n = 3 to n = 2.3 marks
Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).