NCERT Solutions for Class 12 Physics Chapter 10: Wave Optics

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NCERT Solutions for Class 12 Physics Chapter 10 Wave Optics are given in this article. The section of optics dealing with the behaviour of light and its wave characteristics is called wave optics. According to the wave theory of light, light is a form of energy that travels through a medium in the form of a transverse wave.

Class 12 Physics Chapter 10 along with Ray Optics belong to Unit 6 Optics which has a weightage of 18 marks with Unit 5 Electromagnetic Waves in the CBSE Class 12 Physics Exam. NCERT Solutions for Class 12 Physics Chapter 10 deals with multiple phenomena like the Huygens Principle, polarisation, coherent light, diffraction, and brewster’s law where the ray approximation of geometrical optics can not happen, and more.

Download PDF: NCERT Solutions for Class 12 Physics Chapter 10


NCERT Solutions for Class 12 Physics Chapter 10

The NCERT solutions for class 12 physics chapter 10: Wave Optics are given below – 

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Class 12 Physics Chapter 10 – Topics Covered

  • The locus of all the particles that are vibrating in the same phase at any instant is known as wave front.
A wavefront is therefore a surface with the same phase of vibrating particles at any instant of time at every point on it.
  • Huygens’ Principle states – 
    (i) Every point on a wavefront behaves like a source of light and emits secondary wavelets.
    (ii) The secondary wavelets spread in all directions in a vacuum with a speed equal to the velocity of light.
    (iii) The envelope of a wavefront of secondary wavelets, along the forward direction gives the new position of a wavefront.
Huygens’ principle determines the shape of the wave front at any point in time. It allows to determine the shape of the wavefront at a later point of time.
  • When a source of light is a point source, the wavefront is spherical

Amplitude (A) is inversely proportional to the distance x i.e.,

A ∝ 1/x

∴ Intensity (I) ∝ (Amplitude)2

  • When a source of light is linear, the wavefront is cylindrical.

Amplitude (A) ∝ 1/√x

∴ Intensity ∝ (Amplitude)2 ∝ 1 / x

  • Maxwell’s Electromagnetic Wave Theory: Light waves are electromagnetic, therefore, they do not require a material medium for their propagation. Due to its transverse nature, the wave of light undergo polarisation.

The velocity of an electromagnetic wave in a vacuum is:

c = 1/√μo.εo

The velocity of electromagnetic waves in a medium is less than the velocity of light, v < c

v = 1/√μo.εo.εr.μr = c/√μo εr


Previous Year Questions  

  1. When hydrogen atom is in its first excited level, its radius, is….
  2. When an electron does transition from n=4 to n=2 , then emitted line spectrum will be….​..
  3. α -particle consists of….
  4. An electron of a stationary hydrogen atom passes from the fifth energy level….
  5. Complete the equation for the following fission process…. [NEET 1998]
  6. using non-relativistic approach, the speed of electron in this orbit will be…. [NEET 2015]
  7. When the glancing angle of incidence of light on a material is...[COMEDK UGET 2004]
  8. Two waves having intensity ratio 25 : 4 produce interference. The ratio of maximum to minima intensity is...[COMEDK UGET 2004]
  9. In Young's double slit experiment,1st dark fringe occurs directly...[COMEDK UGET 2009]
  10. In the diffraction pattern due to a single slit linear width of the central max...[COMEDK UGET 2007]
  11. In Newton ring experiment, monochromatic light is replaced by white light...[COMEDK UGET 2008]
  12. In diffraction through a single slit experiment, slit width is halved...[COMEDK UGET 2004]
  13. When the angle of incidence on a material is\( 60^{\circ}\)…..[KEAM]
  14. The ratio of the intensities of two waves is 16 : 9. The ratio of their amplitudes is...[KEAM]
  15. In Young’s double slit experimental setup, if the wavelength alone is...[KEAM]
  16. A narrow slit of width 2mm is illuminated by monochromatic light of….[KEAM]
  17. A slit of width a is illuminated by red light of wavelength...[KEAM]
  18. When the experiment is performed in air with same set up, the angular width of the fringe is...[KEAM]
  19. In a Fraunhofer diffraction at single slit of width d with incident light of wavelength...[KEAM]
  20. In Young’s double slit experiment, to increase the fringe width...[KEAM]

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CBSE CLASS XII Related Questions

  • 1.
    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.


      • 2.
        Assertion (A) : The mass of a nucleus is less than the sum of the masses of the constituent nucleons. Reason (R) : Energy is absorbed when the nucleons are bound together to form a nucleus.

          • Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
          • Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
          • Assertion (A) is true, but Reason (R) is false.
          • Both Assertion (A) and Reason (R) are false.

        • 3.
          What is displacement current (\( i_d \))? Considering the case of charging of a capacitor, show that \( i_d = \varepsilon_0 \frac{d\Phi_E}{dt} \). What is the value of \( i_d \) for a conductor across which a constant voltage is applied?


            • 4.
              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

              • 5.
                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.


                  • 6.
                    Assertion (A) : All atoms have a net magnetic moment. Reason (R) : A current loop does not always behave as a magnetic dipole.

                      • Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
                      • Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
                      • Assertion (A) is true, but Reason (R) is false.
                      • Both Assertion (A) and Reason (R) are false.
                    CBSE CLASS XII Previous Year Papers

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