NCERT Solutions For Class 12 Physics Chapter 11: Dual Nature of Radiation and Matter

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Jasmine Grover

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NCERT Solutions for Class 12 Physics Chapter 11 Dual Nature of Radiation and Matter are provided in the article with a detailed explanation of all the concepts. A substance can have wave nature, exhibiting the phenomena of interference and diffraction, as well as a particle nature (quanta or light packets). 

Unit 7 Dual Nature of Radiation and Matter along with Unit 8 Atoms and Nuclei has a weightage of 12 marks in the CBSE Class 12 Physics Examination. NCERT Solutions for Class 12 Physics Chapter 11 covers the concepts of the photoelectric effect and Electron Emission.

Download PDF: NCERT Solutions for Class 12 Physics Dual Nature of Radiation and Matter


NCERT Solutions for Class 12 Physics Chapter 11

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Previous Year Questions

  1.  Which one among the following shows particle nature of light? [ NEET 2001]
  2. The velocity of electron beam will be...[NEET 2001]
  3. aximum torque exerted by the field on the dipole is….[KEAM]
  4. The average velocity and the average speed of the toy car between 0to30to3 seconds are respectively….[NEET 2018]
  5. The energy of most energetic photoelectron is…. [JIPMER 1999]
  6. An example for the best source of monochromatic light is… [JKCET 2019]

Class 12 Physics Chapter 11 – Topics Covered

  • Photoelectric Effect is the phenomenon of emission of photoelectron from the metal surface when a beam of light of suitable frequency is incident on it.

The electrons that are emitted from the surface are known as photoelectrons and the current produced is known as the photoelectric current.

  • Effect of Intensity of Light on Photo current: For a fixed frequency of incident radiation, the photoelectric current linearly increases with an increase in the intensity of incident light.

Effect of Intensity of light on photocurrent

  • Work Function is the minimum amount of energy that is required to eject an electron from the outermost surface of a metal.
\(Work\ Function, W = hv_o\ (threshold\ frequency)= {hc \over \lambda_0 (threshold\ wavelength)}\)
  • For a given frequency of incident radiation, the minimum negative potential V0 given to a plate for which the photoelectric current becomes zero is known as cut-off or stopping potential.
\(KE_{max} = eV_0 => {1 \over 2} mv^2_{max} = eV_0\)
  •  Einstein Photoelectric Equation: When hv is the energy of photon and Ф is the work-function, the equation is given by:
\(K_{max} = hv - \Phi0\)

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CBSE CLASS XII Related Questions

  • 1.
    A circular coil of 100 turns and radius \( \left(\frac{10}{\sqrt{\pi}}\right) \, \text{cm}\) carrying current of \( 5.0 \, \text{A} \) is suspended vertically in a uniform horizontal magnetic field of \( 2.0 \, \text{T} \). The field makes an angle \( 30^\circ \) with the normal to the coil. Calculate:
    the magnetic dipole moment of the coil, and
    the magnitude of the counter torque that must be applied to prevent the coil from turning.


      • 2.
        The magnetic field in a plane electromagnetic wave travelling in glass (\( n = 1.5 \)) is given by \[ B_y = (2 \times 10^{-7} \text{ T}) \sin(\alpha x + 1.5 \times 10^{11} t) \] where \( x \) is in metres and \( t \) is in seconds. The value of \( \alpha \) is:

          • \( 0.5 \times 10^3 \, \text{m}^{-1} \)
          • \( 6.0 \times 10^2 \, \text{m}^{-1} \)
          • \( 7.5 \times 10^2 \, \text{m}^{-1} \)
          • \( 1.5 \times 10^3 \, \text{m}^{-1} \)

        • 3.
          The figure represents the variation of the electric potential \( V \) at a point in a region of space as a function of its position along the x-axis. A charged particle will experience the maximum force at:

            • P
            • Q
            • R
            • S

          • 4.
            The energy of an electron in an orbit in hydrogen atom is \( -3.4 \, \text{eV} \). Its angular momentum in the orbit will be:

              • \( \dfrac{3h}{2\pi} \)
              • \( \dfrac{2h}{\pi} \)
              • \( \dfrac{h}{\pi} \)
              • \( \dfrac{h}{2\pi} \)

            • 5.

              The electric potential (V ) and electric field (⃗ E) are closely related concepts in electrostatics. The electric field is a vector quantity that represents the

                • Production of AC is economical.
                • AC can be easily and efficiently converted from one voltage to another.
                • AC can be transmitted economically over long distances.
                • AC is less dangerous.

              • 6.
                Four long straight thin wires are held vertically at the corners A, B, C and D of a square of side \( a \), kept on a table and carry equal current \( I \). The wire at A carries current in upward direction whereas the current in the remaining wires flows in downward direction. The net magnetic field at the centre of the square will have the magnitude:

                  • \( \dfrac{\mu_0 I}{\pi a} \) and directed along OC
                  • \( \dfrac{\mu_0 I}{\pi a \sqrt{2}} \) and directed along OD
                  • \( \dfrac{\mu_0 I \sqrt{2}}{\pi a} \) and directed along OB
                  • \( \dfrac{2\mu_0 I}{\pi a} \) and directed along OA
                CBSE CLASS XII Previous Year Papers

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