Bohr model, energy levels, hydrogen spectrum
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See all →- A model for quantized motion of an electron in a uniform magnetic field B states that the flux passing through the orbit of the electron is n(h/e) where n is an integer, h is Planck's constant and e is the magnitude of electron's charge. According to… Answer: 2. he/2π m Key idea: the electron moves in a circle in the field, and the given flux quantization fixes the orbit area. From evB=mv²... 1
- A particle of mass m is moving around the origin with a constant force F pulling it towards the origin. If Bohr model is used to describe its motion, the radius r of the n^th orbit and the particle's speed v in the orbit depend on n as Answer: 3. r ∝ n^(2/3);\ v ∝ n^(1/3) Key idea: apply Newton's second law with the constant force as the centripetal force, together with Boh... 1
- Match List I with List II.List I (Spectral Lines of Hydrogen for transitions from): A. n_2=3 to n_1=2; B. n_2=4 to n_1=2; C. n_2=5 to n_1=2; D. n_2=6 to n_1=2List II (Wavelengths (nm)): I. 410.2; II. 434.1; III. 656.3; IV. 486.1Choose the correct ans… Answer: 3. A-III, B-IV, C-II, D-I Key idea: These are Balmer lines (transitions to n=2 ); a larger jump means more energy and a shorter wave... 1
- The radius of inner most orbit of hydrogen atom is 5.3×10^-11 m. What is the radius of third allowed orbit of hydrogen atom? Answer: 1. 4.77 mathringA Bohr orbit radius: r_n=n² r₁ . Third orbit: r₃=9×5.3×10⁻¹¹=4.77×10⁻¹⁰ m = 4.77 Å (1 Å = 10⁻¹⁰ m). 1
- In hydrogen spectrum, the shortest wavelength in the Balmer series is λ. The shortest wavelength in the Bracket series is : Answer: 3. 4λ The shortest wavelength of a series comes from the transition from n=∞ to the series' lower level n₁ : dfrac1λ=R/n₁² , so λ∝ n... 1
- Let T_1 and T_2 be the energy of an electron in the first and second excited states of hydrogen atom, respectively. According to the Bohr's model of an atom, the ratio T_1 : T_2 is : Answer: 1. 9 : 4 In Bohr's model the energy magnitude is E_n∝ 1/n² . First excited state is n=2 and second excited state is n=3 . T₁/T₂=1/4/... 1