NCERT Solutions for Class 12 Physics Chapter 12: Atoms

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NCERT Solutions for Class 12 Physics Chapter 12 Atoms are given in this article. Atoms are the smallest unit into which matter can be divided without the release of electrically charged particles. It also is the smallest unit of matter that has the characteristic properties of a  chemical element. Atom is the basic building block of chemistry.

Unit 8 Atoms and Nuclei along with Unit 7 Dual Nature of Radiation and Matter has a weightage of 12 marks in the CBSE Board examinations. The Class 12 Physics Chapter 12 NCERT Solutions cover the concepts of Atomic SpectraMagnetic Quantum Number, and energy levels.

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NCERT Solutions for Class 12 Physics Chapter 12

The NCERT solutions for Class 12 Physics Chapter 12: Atoms is given below. 

 NCERT SolutionsNCERT SolutionsNCERT SolutionsNCERT SolutionsNCERT SolutionsNCERT Solutions


CBSE Class 12 Physics Chapter 12 – Topics Covered

  • Thomson’s Atomic Model: Every atom is a uniformly positive charged sphere of radius of the order of 10-10 m, in which the entire mass is distributed uniformly and negatively charged electrons are randomly embedded randomly. 

Limitations of Thomson’s Atomic Model

1. It couldn’t explain the origin of spectral series of hydrogen and other atoms.

2. It couldn’t explain the large angle scattering of α-particles.

  • Bohr Model of the Hydrogen AtomAn electron can revolve in certain non-radiating orbits for which the angular momentum of electron is an integer multiple of (h/2π).
\(r_n = n^2({h^2 \epsilon_o \over \pi mZe^2})\)
  • Hydrogen Spectrum Series: Each element emits a radiation spectrum, which is characteristic of the element itself. The spectrum is known as the line spectrum.

Hydrogen spectrum consists of 5 series – Lyman Series, Balmer Series, Paschen Series, Brackett Series, and Pfund Series.
  • Wave Model is based on wave mechanics. Quantum numbers are the numbers that are required to completely specify the state of the electrons.

In the presence of a strong magnetic field, the 4 quantum number are Principle quantum number, Orbital angular momentum quantum number, Magnetic quantum number, and Magnetic spin angular momentum quantum number.

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CBSE CLASS XII Related Questions

  • 1.
    If Bohr’s quantization postulate (angular momentum \( = \frac{nh}{2\pi} \)) 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 quantization of orbits of planets around the Sun? Explain.


      • 2.
        Draw the number of scattered particles versus the scattering angle graph for scattering of alpha particles by a thin foil. Write two important conclusions that can be drawn from this plot.


          • 3.
            Four independent waves are expressed as \[ (i)\; y_1=A_1\sin\omega t, \] \[ (ii)\; y_2=A_2\sin 2\omega t, \] \[ (iii)\; y_3=A_3\cos\omega t, \] \[ (iv)\; y_4=A_4\sin\left(\omega t+\frac{\pi}{3}\right) \] The interference between two of these waves is possible in

              • (i) and (iii) only
              • (iii) and (iv) only
              • (i), (iii) and (iv) only
              • All of them

            • 4.
              The figure shows three point charges kept at the vertices of triangle ABC. The net electric field, due to this system of charges, at the midpoint M of base BC will be:

                • \( \frac{q}{4 \pi \epsilon_0 l^2} \) pointing along MA
                • \( \frac{q}{\pi \epsilon_0 l^2} \) pointing along AM
                • \( \frac{q}{2 \pi \epsilon_0 l^2} \) pointing along AM
                • Zero

              • 5.
                Draw a circuit diagram of a full-wave rectifier using p-n junction diodes. Explain its working and show the input-output waveforms.


                  • 6.
                    Write the expression for the magnetic field due to a current element in vector form. Consider a 1 cm segment of a wire, centered at the origin, carrying a current of 10 A in positive x-direction. Calculate the magnetic field \( \mathbf{B} \) at a point \( (1 \, \text{m}, 1 \, \text{m}, 0) \).

                      CBSE CLASS XII Previous Year Papers

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