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IB · E · multiple choice

Nuclear and quantum physics · Question 1

Nuclear and quantum physics · Original GioPhysics question with a detailed, mark-by-mark answer guide.

Demand
demanding
Marks
1
Topics
1
Answer
Complete
Energy levels of the hydrogen atom, with one transition markedenergyn = ∞n = 4n = 3n = 2n = 10 eV−0.85 eV−1.51 eV−3.40 eV−13.6 eVelectron transitionnot to scale
Fig. 1.1An energy level diagram for a hydrogen atom, drawn not to scale, with energy increasing up the page. Five horizontal levels are shown: the ground state n = 1 at −13.6 eV, then n = 2 at −3.40 eV, n = 3 at −1.51 eV, n = 4 at −0.85 eV, and n = ∞ at 0 eV. A vertical arrow drawn between the −1.51 eV level and the −3.40 eV level points downwards, marking the electron transition the question describes.
multiple choice1 mark

An electron in a hydrogen atom moves from an energy level of −1.51 eV to a level of −3.40 eV. What is the wavelength of the emitted photon? (hc = 1240 eV nm)

  1. A

    254 nm

  2. B

    365 nm

  3. C

    656 nm

  4. D

    821 nm

Ready to self-mark?Reveal the detailed answer guide
Answer overviewCorrect answer: C — 656 nm
01

Answer and reasoning

1 mark
How to approach it

Predict from the governing principle before looking for a matching option. Then reject alternatives by checking direction, units, limiting behaviour or the physical meaning of each statement.

  1. 1

    The correct choice is C: 656 nm

  2. 2

    The photon energy is the difference between the levels, 1.89 eV, giving 1240/1.89 = 656 nm. B uses 3.40 eV and D uses 1.51 eV — both are the answers of a candidate who uses one level rather than the gap between them.

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