Free Atomic Spectra MCQs with Answers
356 Atomic Spectra MCQs from Physics, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Atoms emit or absorb light at specific wavelengths because electrons occupy quantized energy levels and change levels by absorbing or releasing photons. The topic covers emission and absorption spectra, spectral series, hydrogen’s line spectrum, energy-level transitions, and the relation between wavelength, frequency and photon energy.
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Read the Atomic Spectra notesFree MDCAT chapter notes with key terms356 questions · page 7 of 18
- A. 10^-35 sec:**
- B. 10^-8 sec:**
- C. 10^-3 sec
- D. 0.1 sec
Explanation: Correct. The lifetime of an ordinary excited state is typically on the order of 0.1 secondsIn summary, the correct option is **d.
Correct answer: 0.1 sec- A. 6
- B. 4
- C. 10
- D. 3
Explanation: The maximum number of transitions from \(n = 5\) occurs when the atom transitions to all lower energy states (\(n' = 4, 3, 2, 1\))…
Correct answer: 4- A. Penetrating power of X-rays increases
- B. Intensity of X-rays increases
- C. Wavelength of X-rays increases
- D. All of these
Explanation: Increasing the voltage results in higher-energy X-rays with greater penetrating power.
Correct answer: Penetrating power of X-rays increases- A. Ionized state
- B. Stimulation state
- C. Population state
- D. All of these
Explanation: In population inversion, the metastable state contains more electrons than the ground state.
Correct answer: Population state- A. Ground state
- B. Ionized state
- C. Metastable state
- D. Ordinary excited state
Explanation: A metastable state is an excited state of an atom or molecule that has a longer-than-average lifetime before spontaneously transitioning…
Correct answer: Metastable state- A. Balmer
- B. Paschen
- C. Pfund
- D. Humphery
Explanation: The formula for spectral lines is:1/λ = RH (1/nl2 - 1/nh2)Where nl = lower orbit nh = higher orbitThe series are in the…
Correct answer: Humphery- A. UV
- B. Visible
- C. Infrared
- D. None of these
Explanation: The Balmer series results from electron transitions from higher energy states (n=3,4,5,..) to n=2, with wavelengths in the visible…
Correct answer: Visible- A. 4/RH
- B. 9/RH
- C. 16/RH
- D. 25/RH
Explanation: For the Pfund series, 1/λ = RH (1/5² - 1/n²). Shortest wavelength occurs when n=∞, so 1/λ = RH/5², λ = 5²/RH.
Correct answer: 25/RH- A. Kα
- B. Kβ
- C. Both A and B
- D. None of the above
Explanation: Kα energy (EL - EK) is less than Kβ energy (EM - EK), as Kβ involves an electron transition from the M shell to the K shell.
Correct answer: Kβ- A. Characteristic X-ray
- B. Continuous X-ray
- C. Both A and B
- D. None of the above
Explanation: Hard X-rays are continuous X-rays, produced when electrons lose energy, resulting in higher energy than characteristic X-rays.
Correct answer: Continuous X-ray- A. 5.41 Å
- B. 4.20 Å
- C. 2.70 Å
- D. 1.35 Å
Explanation: Using Moseley's law, λ₂/λ₁ = (Z₁ - B)²/(Z₂ - B)². For platinum (Z₁=78, λ₁=1.30 Å) and molybdenum (Z₂=42), λ₂ = [(78 - 7.4)²/(42-7.4)²] ×…
Correct answer: 5.41 Å132. When a hydrogen atom is in its first excited level, what is the relation of radius and Bohr radius?
- A. Twice
- B. Four times
- C. Same
- D. Half
Explanation: For the first excited level (n=2), radius r₂ = n²r₀ = 2²r₀ = 4r₀, where r₀ is the Bohr radius.
Correct answer: Four times- A. 0.85 eV
- B. 3.4 eV
- C. 13.6 eV
- D. 12.1 eV
Explanation: The third excited state is n=4. Ionization energy = E₀/n² = 13.6/4² = 13.6/16 = 0.85 eV.
Correct answer: 0.85 eV- A. p, p+1, p+2...
- B. p+1, p+2...
- C. p, p-1, p-2...
- D. p-1, p-2...
Explanation: In the Rydberg formula, p is the lower energy state, and n is the higher state (n > p). Thus, n = p+1, p+2, ... for emission.
Correct answer: p+1, p+2...- A. Visible
- B. Ultraviolet
- C. Infrared
- D. Red
Explanation: The Lyman series, from higher states to n=1, has high-frequency photons in the ultraviolet region.
Correct answer: Ultraviolet- A. 2
- B. 4
- C. 3
- D. 6
Explanation: Number of spectral lines = n(n-1)/2. For n=4, 4(4-1)/2 = 6. Alternatively, transitions are 4→3, 4→2, 4→1, 3→2, 3→1, 2→1, totaling 6 lines.
Correct answer: 6- A. First orbit
- B. Third orbit
- C. Second orbit
- D. Fourth orbit
Explanation: The Brackett series corresponds to electron transitions from higher energy levels n ≥ 5 down to n = 4.
Correct answer: Fourth orbit- A. One
- B. Three
- C. Two
- D. Four
Explanation: The three types of emission spectra are line spectrum, band spectrum, and continuous spectrum.
Correct answer: Three- A. Increases
- B. Decreases
- C. Unchanged
- D. May decrease or increase
Explanation: The number of spectral lines decreases from the Lyman series (n=1) to the Pfund series (n=5) as energy level spacing decreases with higher…
Correct answer: Decreases- A. R to S
- B. Q to R
- C. R to G
- D. P to Q
Explanation: If E is the energy radiated in transition then ER→G > EQ→S > EQ→R > EP→Q. For getting blue line energy radiated should be maximum (E = 1/λ).
Correct answer: R to G