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 long solenoid of length \( L \) and radius \( r_1 \) having \( N_1 \) turns is surrounded symmetrically by a coil of radius \( r_2 \, (r_2>r_1) \) having \( N_2 \) turns (\( N_2 \ll N_1 \)) around its mid-point. Derive an expression for the mutual inductance of solenoid and coil. Is \( M_{12} = M_{21} \) valid in this case?


      • 2.
        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 \( (1 \, \text{m}, 1 \, \text{m}, 0) \).


          • 3.
            If both the number of protons and the neutrons are conserved in each nuclear reaction, in what way is mass converted into energy (or vice versa) in a nuclear reaction? Explain.


              • 4.
                Photoemission of electrons occurs from a metal (\( \phi_0 = 1.96 \, \text{eV} \)) when light of frequency \( 6.4 \times 10^{14} \, \text{Hz} \) is incident on it. Calculate: Energy of a photon in the incident light, The maximum kinetic energy of the emitted electrons, and The stopping potential.


                  • 5.
                    Two thin lenses of focal length \( f_1 \) and \( f_2 \) are placed in contact with each other coaxially. Prove that the focal length \( f \) of the combination is given by \[ f = \frac{f_1 f_2}{f_1 + f_2}. \]


                      • 6.
                        Two parallel plate capacitors X and Y are connected in series to a 6 V battery. They have the same plate area and same plate separation but capacitor X has air between its plates, whereas capacitor Y contains a material of dielectric constant 4. Calculate the capacitances of X and Y, if the equivalent capacitance of the combination of X and Y is \( 4 \, \mu\text{F} \). Calculate the potential difference across the plates of X and Y.

                          CBSE CLASS XII Previous Year Papers

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