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Atoms Physics - Atoms

Bihar Board (BSEB) - STD 12 Science - Physics (BSEB - English Medium). 406 questions in this chapter.

Question types

Atoms question types

406 questions across 7 question groups — pick any mix to generate a Physics paper with step-by-step answer keys.

406
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7
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5
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Sample Questions

Atoms 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 [1M]1 Mark
Which of the following statements is not correct according to Rutherford model?
  • A
    Most of the space inside an atom is empty.
  • B
    The electrons revolve around the nucleus under the influence of coulomb force acting on them.
  • C
    Most part of the mass of the atom and its positive charge are concentrated at its centre.
  • D
    The stability of atom was established by the model.
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Q 2M.C.Q [1M]1 Mark
The value of scattering angle of alpha particle for minimum value of impact parameter is-
  • ✓
    $180^{\circ}$
  • B
    $90^{\circ}$
  • C
    $0^{\circ}$
  • D
    $120^{\circ}$

Answer: A.

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Q 4M.C.Q [1M]1 Mark
The ground state energy of hydrogen atom is -13.6 eV. The kinetic and potential energies of the electron in this state are:
  • A
    -13.6 eV, 27.2 eV
  • B
    13.6 eV,-13.6 eV
  • C
    13.6 eV,-27.2 eV
  • D
    27.2 eV,-27.2 eV
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Q 5M.C.Q [1M]1 Mark
The property of cathode rays used in the monitor of a computer is:
  • A
    High velocity of the rays
  • B
    High ionization power of the rays
  • C
    The property to cause fluorescence
  • D
    Rectilinear propagation
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Q 6Assertion (A) & Reason (B) MCQ1 Mark
For question two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.

  1. Both A and R are true, and R is the correct explanation of A.
  2. Both A and R are true, but R is NOT the correct explanation of A.
  3. A is true, but R is false.
  4. A is false and R is also false.

Assertion (A): The positively charged nucleus of an atom has a radius of almost 10-15m.

Reason (R): In $\alpha$-particle scattering experiment, the distance of closest approach for $\alpha$-particles is 10-15m.

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Q 7Assertion (A) & Reason (B) MCQ1 Mark
For question two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.

  1. Both A and R are true, and R is the correct explanation of A.
  2. Both A and R are true, but R is NOT the correct explanation of A.
  3. A is true, but R is false.
  4. A is false and R is also false.

Assertion (A): Total energy of electron in an hydrogen atom is negative.

Reason (R): It is bounded to the nucleus.

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Q 8Assertion (A) & Reason (B) MCQ1 Mark
For question two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.

  1. Both A and R are true, and R is the correct explanation of A.
  2. Both A and R are true, but R is NOT the correct explanation of A.
  3. A is true, but R is false.
  4. A is false and R is also false.

Assertion (A): Fraunhofer lines are observed in the spectrum of the sun.

Reason (R): The different elements have different spectra.

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Q 9Assertion (A) & Reason (B) MCQ1 Mark
For question two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
  1. Both A and R are true, and R is the correct explanation of A.
  2. Both A and R are true, but R is NOT the correct explanation of A.
  3. A is true, but R is false.
  4. A is false and R is also false.
Assertion (A): An electron in hydrogen atom passes from n = 4 to n = 1 level. The maximum number of photons that can be emitted is 4.
Reason (R): Maximum number of photons emitted can only be 4
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Q 10Assertion (A) & Reason (B) MCQ1 Mark
For question two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
  1. Both A and R are true, and R is the correct explanation of A.
  2. Both A and R are true, but R is NOT the correct explanation of A.
  3. A is true, but R is false.
  4. A is false and R is also false.
Assertion (A): In He-Ne laser, population inversion takes place between energy levels of neon atoms.
Reason (R): Helium atoms have a meta-stable energy level.
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Q 111 Marks Question1 Mark
Choose the correct alternative from the clues given at the end of the each statement:
A classical atom based on .......... is doomed to collapse. (Thomson’s model/ Rutherford’s model.)
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Q 121 Marks Question1 Mark
Choose the correct alternative from the clues given at the end of the each statement:
The size of the atom in Thomson’s model is .......... the atomic size in Rutherford’s model. (much greater than/ no different from/ much less than.)
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Q 131 Marks Question1 Mark
Answer the following questions, which help you understand the difference between Thomson’s model and Rutherford’s model better.

Keeping other factors fixed, it is found experimentally that for small thickness t, the number of α-particles scattered at moderate angles is proportional to t. What clue does this linear dependence on t provide?

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Q 141 Marks Question1 Mark
Answer the following questions, which help you understand the difference between Thomson’s model and Rutherford’s model better.
Is the probability of backward scattering (i.e., scattering of α-particles at angles greater than 90°) predicted by Thomson’s model much less, about the same, or much greater than that predicted by Rutherford’s model?
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Q 151 Marks Question1 Mark
Answer the following questions, which help you understand the difference between Thomson’s model and Rutherford’s model better.
Is the average angle of deflection of α-particles by a thin gold foil predicted by Thomson’s model much less, about the same, or much greater than that predicted by Rutherford’s model?
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Q 16Short Answer Type Questions [2M]2 Marks
Define the distance of closest approach. An α-particle of kinetic energy 'K' is bombarded on a thin gold foil. The distance of the closest approach is 'r'. What will be the distance of closest approach for an α-particle of double the kinetic energy?
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Q 17Short Answer Type Questions [2M]2 Marks
Suppose you are given a chance to repeat the alpha-particle scattering experiment using a thin sheet of solid hydrogen in place of the gold foil. (Hydrogen is a solid at temperatures below 14 K.) What results do you expect?
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Q 20Short Answer Type Questions [2M]2 Marks
If Bohr’s quantisation postulate (angular momentum $=\text{nh}/\pi$) is a basic law of nature, it should be equally valid for the case of planetary motion also. Why then do we never speak of quantisation of orbits of planets around the sun?
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Q 213 Marks Question3 Marks
The total energy of an electron in the first excited state of the hydrogen atom is about –3.4 eV.
  1. What is the kinetic energy of the electron in this state?
  2. What is the potential energy of the electron in this state?
  3. Which of the answers above would change if the choice of the zero of potential energy is changed?
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Q 223 Marks Question3 Marks
Obtain the first Bohr’s radius and the ground state energy of a muonic hydrogen atom [i.e., an atom in which a negatively charged muon $(\mu)$ of mass about 207me orbits around a proton].
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Q 233 Marks Question3 Marks
A difference of 2.3 eV separates two energy levels in an atom. What is the frequency of radiation emitted when the atom make a transition from the upper level to the lower level?
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Q 243 Marks Question3 Marks
In accordance with the Bohr’s model, find the quantum number that characterises the earth’s revolution around the sun in an orbit of radius 1.5 × 1011 m with orbital speed 3 × 104 m/s. (Mass of earth = 6.0 × 1024 kg.)
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Q 264 Marks Questions4 Marks
When the electron orbiting in hydrogen atom in its ground state moves to the third excited state, show how the de Broglie wavelength associated with it would be affected.
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Q 274 Marks Questions4 Marks
  1. The figure shows the plot of binding energy (BE) per nucleon as a function of mass number A. The letters A, B, C, D and E represent the positions of typical nuclei on the curve. Point out, giving reasons, the two processes (in terms of A, B, C, D and E), one of which can occur due to nuclear fission and the other due to nuclear fusion.

  1. Identify the nature of the radioactive radiations emitted in each step of the decay process given below.

$^{A}_{Z}\text{X}\rightarrow ^{A-4}_{Z-2}\text{Y}\rightarrow ^{A-4}_{Z-1}\text{W}$.

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Q 284 Marks Questions4 Marks
In the study of Geiger-Marsdon experiment on scattering of α  particles by a thin foil of gold, draw the trajectory ofα−particles in the Coulomb field of target nucleus. Explain briefly how one gets the information on the size of the nucleus from this study. From the relation R = R0 A1/3, where R0 is constant and A is the mass number of the nucleus, show that nuclear matter density is independent of A.
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Q 294 Marks Questions4 Marks
Niels Bohr introduced the atomic Hydrogen model in 1913. He described it as a positively charged nucleus, comprised of protons and neutrons, surrounded by a negatively charged electron cloud. In the model, electrons orbit the nucleus in atomic shells. The atom is held together by electrostatic forces between the positive nucleus and negative surroundings.

Bohr correctly proposed that the energy and radii of the orbits of electrons in atoms are quantized, with energy for transitions between orbits given by
$\triangle\text{E}=\text{h}\upsilon=\text{E}_\text{i}-\text{E}_\text{f}$ where $\triangle\text{E}$ is the change in energy between the initial and final orbits and $\text{h}\upsilon$ is the energy of an absorbed or emitted photon.
  1. In the Bohr model of the hydrogen atom, discrete radii and energy states result when an electron circles the atom in an integer number of
  1. De Broglie wavelengths
  2. Wave frequencies
  3. Quantum numbers
  4. Diffraction patterns.
  1. The angular speed of the electron in the nth orbit of Bohr's hydrogen atom is.
  1. Directly proportional to n
  2. Inversely proportional to $\sqrt{\text{n}}$
  3. Inversely proportional to n2
  4. Inversely proportional to n3
  1. When electron jumps from n = 4 level to n = 1 level, the angular momentum of electron changes by.
  1. $\frac{\text{h}}{2\pi}$
  2. $\frac{\text{h}}{\pi}$
  3. $\frac{\text{3h}}{2\pi}$
  4. $\frac{\text{2h}}{\pi}$
  1. The lowest Bohr orbit in hydrogen atom has.
  1. The maximum energy
  2. The least energy
  3. Infinite energy
  4. Zero energy
  1. Which of the following postulates of the Bohr model led to the quantization of energy of the hydrogen atom?
  1. The electron goes around the nucleus in circular orbits.
  2. The angular momentum of the electron can only be an integral multiple of $\frac{\text{h}}{2\pi}$.
  3. The magnitude of the linear momentum of the electron is quantized.
  4. Quantization of energy is itself a postulate of the Bohr model.
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Q 304 Marks Questions4 Marks

In 1911, Rutherford, along with his assistants, H. Geiger and E. Marsden, performed the alpha particle scattering experiment. H. Geiger and E. Marsden took radioactive source $(^{214}_{83}\text{Bi})$ for $\alpha$- particles. A collimated beam of $\alpha$-particles of energy 5.5 MeV was allowed to fall on 2.1 × 10-7 m thick gold foil. The $\alpha$-particles were observed through a rotatable detector consisting of a Zinc sulphide screen and microscope. It was found that CL-particles got scattered. These scattered $\alpha$-particles produced scintillations on the zinc sulphide screen. Observations of this experiment are as follows?

Most of the $\alpha$-particles passed through the foil without deflection.

Only about 0.14% of the incident $\alpha$-particles scattered by more than 1º

Only about one $\alpha$-particle in every 8000 $\alpha$-particles deflected by more than 90º

These observations led to many arguments and conclusions which laid down the structure of the nuclear model of an atom.

  1. Rutherford's atomic model can be visualised as.

  1. Gold foil used in Geiger-Marsden experiment is about 10-8 m thick. This ensures.
  1. Gold foil's gravitational pull is small or possible.
  2. Gold foil is deflected when $\alpha$-particle stream is not incident centrally over it.
  3. Gold foil provides no resistance to passage of $\alpha$-particles.
  4. Most $\alpha$-particle will not suffer more than 1º scattering during passage through gold foil.
  1. In Geiger-Marsden scattering experiment, the trajectory traced by an $\alpha$-particle depends on.
  1. Number of collision.
  2. Number of scattered $\alpha$- particles.
  3. Impact parameter.
  4. None of these.
  1. In the Geiger-Marsden scattering experiment, in case of head-on collision, the impact parameter should be.
  1. Maximum
  2. Minimum
  3. Infinite
  4. zero
  1. The fact only a small fraction of the number of incident particles rebound back in Rutherford scattering indicates that.
  1. Number of $\alpha$-particles undergoing head-on-collision is small.
  2. Mass of the atom is concentrated in a small volume.
  3. Mass of the atom is concentrated in a large volume.
  4. Both (a) and (b).
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Q 32Long Answer Type Questions [5M]5 Marks
Classically, an electron can be in any orbit around the nucleus of an atom. Then what determines the typical atomic size? Why is an atom not, say, thousand times bigger than its typical size? The question had greatly puzzled Bohr before he arrived at his famous model of the atom that you have learnt in the text. To simulate what he might well have done before his discovery, let us play as follows with the basic constants of nature and see if we can get a quantity with the dimensions of length that is roughly equal to the known size of an atom (~ 10–10m).
  1. Construct a quantity with the dimensions of length from the fundamental constants e, me, and c. Determine its numerical value.
  2. You will find that the length obtained in (a) is many orders of magnitude smaller than the atomic dimensions. Further, it involves c. But energies of atoms are mostly in non-relativistic domain where c is not expected to play any role. This is what may have suggested Bohr to discard c and look for ‘something else’ to get the right atomic size. Now, the Planck’s constant h had already made its appearance elsewhere. Bohr’s great insight lay in recognising that h, me, and e will yield the right atomic size. Construct a quantity with the dimension of length from h, me, and e and confirm that its numerical value has indeed the correct order of magnitude.
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Q 35Long Answer Type Questions [5M]5 Marks
The gravitational attraction between electron and proton in a hydrogen atom is weaker than the coulomb attraction by a factor of about 10–40. An alternative way of looking at this fact is to estimate the radius of the first Bohr orbit of a hydrogen atom if the electron and proton were bound by gravitational attraction. You will find the answer interesting.
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