ECAT Physics — Atomic Spectra
Atomic Spectra is part of the Physics section of the UET ECAT (30 of the 100 MCQs). It breaks into 3 subtopics, and we hold 13 ECAT-pattern practice MCQs on it, each with a written explanation. Tap a subtopic below to practise just that.
Subtopics (3)
How Atomic Spectra is tested
Across the 7 ECAT past papers on ParhaiKrlo, Atomic Spectra accounts for 3 questions. It appears in 3 of them, about 1 questions a paper. The heaviest was ECAT Past Paper 05, with 1 question.
| Paper | Questions |
|---|---|
| ECAT Past Paper 05 | 1 |
| ECAT Past Paper 03 | 1 |
| ECAT Past Paper 01 | 1 |
Atomic Spectra MCQs from the ECAT past papers
Try each one before opening the answer. Each comes with a short explanation.
- Q1 · ECAT Past Paper 05 · Atomic Spectra
When the spectrum of the hydrogen atom is taken in a magnetic field, some new lines appear. This is called the:
- A.Resonance effect
- B.Zeeman effect
- C.Stark effect
- D.Electric effect
Show answer
Answer: B. Zeeman effect — Splitting of spectral lines in a magnetic field is the Zeeman effect (in an electric field, the Stark effect).
- Q2 · ECAT Past Paper 03 · Atomic Spectra
High-energy photons emitted due to transitions of inner-shell electrons in heavy atoms are called:
- A.Characteristic X-rays
- B.Heavy photons
- C.Continuous X-rays
- D.K photons
Show answer
Answer: A. Characteristic X-rays — Inner-shell transitions emit X-rays of fixed energies typical of the element: characteristic X-rays.
- Q3 · ECAT Past Paper 01 · Atomic Spectra
The wave number of a light wave is 5 × 10⁶ m⁻¹. Its wavelength is:
- A.2 × 10⁷ m
- B.2 × 10⁻⁷ m
- C.5 × 10⁻⁸ m
- D.None of these
Show answer
Answer: B. 2 × 10⁻⁷ m — Wave number = 1/λ, so λ = 1/(5 × 10⁶) = 2 × 10⁻⁷ m.