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Bohr’s Model and Physics of Atom Physics - Bohr’s Model and Physics of Atom

Uttarakhand Board (UBSE) - STD 12 Science - Physics (Uttarakhand - English Medium). 72 questions in this chapter.

Question types

Bohr’s Model and Physics of Atom question types

72 questions across 6 question groups — pick any mix to generate a Physics paper with step-by-step answer keys.

72
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6
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5
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Sample Questions

Bohr’s Model and Physics of Atom questions

One sample from each question group in this chapter. Select any group above to see the full set with answer keys.

Q 1M.C.Q (1 Marks)1 Mark
The minimum orbital angular momentum of the electron in a hydrogen atom is:
  • A
    $\text{h}$
  • B
    $\frac{\text{h}}{2}$
  • ✓
    $\frac{\text{h}}{2\pi}$
  • D
    $\frac{\text{h}}{\lambda}$

Answer: C.

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Q 2M.C.Q (1 Marks)1 Mark
In which of the following systems will the wavelength corresponding to $n = 2$ to $n = 1$ be minimum?
  • A
    Hydrogen atom.
  • B
    Deuterium atom.
  • C
    Singly ionized helium.
  • ✓
    Doubly ionized lithium.

Answer: D.

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Q 4M.C.Q (1 Marks)1 Mark
Three photons coming from excited atomic-hydrogen sample are picked up. Their energies are 12.1eV, 10.2 eV and 1.9eV. These photons must come from:
  • A
    A single atom.
  • B
    Two atoms.
  • C
    Three atoms.
  • ✓
    Either two atoms or three atoms.

Answer: D.

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Q 5M.C.Q (1 Marks)1 Mark
In which of the following systems will the radius of the first orbit $(n = 1)$ be minimum?
  • A
    Hydrogen atom.
  • B
    Deuterium atom.
  • C
    Singly ionized helium.
  • ✓
    Doubly ionized lithium.

Answer: D.

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Q 72 Marks Questions2 Marks
A spectroscopic instrument can resolve two nearby wavelengths $\lambda$ and $\lambda+\Delta\lambda$ if $\frac{\lambda}{\Delta\lambda}$ is smaller than 8000. This is used to study the spectral lines of the Balmer series of hydrogen. Approximately how many lines will be resolved by the instrument?
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Q 82 Marks Questions2 Marks
Suppose, in certain conditions only those transitions are allowed to hydrogen atoms in which the principal quantum number n changes by 2. (a) Find the smallest wavelength emitted by hydrogen. (b) List the wavelength emitted by hydrogen in the visible range (380nm to 780nm).
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Q 92 Marks Questions2 Marks
The light emitted in the transition n = 3 to n = 2 in hydrogen is called $\text{H}_\alpha$ light. Find the maximum work function a metal can have so that $\text{H}_\alpha$ light can emit photoelectrons from it.
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Q 112 Marks Questions2 Marks
A filter transmits only the radiation of wavelength greater than 440nm. Radiation from a hydrogen-discharge tube goes through such a filter and is incident on a metal of work function 2.0eV. Find the stopping potential which can stop the photoelectrons.
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Q 123 Marks Question3 Marks
Find the temperature at which the average thermal kinetic energy is equal to the energy needed to take a hydrogen atom from its ground state to n = 3 state. Hydrogen can now emit red light of wavelength 653.1nm. Because of Maxwellian distribution of speeds, a hydrogen sample emits red light at temperatures much lower than that obtained from this problem. Assume that hydrogen molecules dissociate into atoms.
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Q 143 Marks Question3 Marks
A hydrogen atom in state n = 6 makes two successive transitions and reaches the ground state. In the first transition a photon of 1.13eV is emitted. (a) Find the energy of the photon emitted in the second transition (b) What is the value of n in the intermediate state?
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Q 153 Marks Question3 Marks
Which wavelengths will be emitted by a sample of atomic hydrogen gas (in ground state) if electrons of energy 12.2eV collide with the atoms of the gas?
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Q 163 Marks Question3 Marks
The first excited energy of a $He^+$ ion is the same as the ground state energy of hydrogen. Is it always true that one of the energies of any hydrogen-like ion will be the same as the ground state energy of a hydrogen atom?
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Q 175 Marks Questions5 Marks
Consider an excited hydrogen atom in state n moving with a velocity u(ν << c). It emits a photon in the direction of its motion and changes its state to a lower state m. Apply momentum and energy conservation principles to calculate the frequency ν of the emitted radiation. Compare this with the frequency $ν_0$ emitted if the atom were at rest.
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Q 185 Marks Questions5 Marks
Radiation coming from transition n = 2 to n = 1 of hydrogen atoms falls on helium ions in n = 1 and n = 2 states. What are the possible transitions of helium ions as they absorbs energy from the radiation?
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Q 205 Marks Questions5 Marks
A beam of monochromatic light of wavelength $\lambda$ ejects photoelectrons from a cesium surface $\big(\Phi=1.9\text{eV}\big).$ These photoelectrons are made to collide with hydrogen atoms in ground state. Find the maximum value of $\lambda$ for which (a) hydrogen atoms may be ionized, (b) hydrogen atoms may get excited from the ground state to the first excited state and (c) the excited hydrogen atoms may emit visible light.
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Q 215 Marks Questions5 Marks
What will be the energy corresponding to the first excited state of a hydrogen atom if the potential energy of the atom is taken to be 10eV when the electron is widely separated from the proton? Can we still write $\text{E}_\text{n}=\frac{\text{E}_1}{\text{n}^2}?\text{ r}_\text{n}=\text{a}_0\text{n}^2?$
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Q 23Case study (4 Marks)4 Marks
Suppose in an imaginary world the angular momentum is quantized to be even integral multiples of $\frac{\text{h}}{2\pi}$ What is the longest possible wavelength emitted by hydrogen atoms in visible range in such a world according to Bohr's model?
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