NCERT Solutions For Class 12 Physics Chapter 8: Electromagnetic Waves

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NCERT Solutions for Class 12 Physics Chapter 8 Electromagnetic Waves are provided in this article. The waves that are produced when an electric field comes into contact with a magnetic field are known as Electromagnetic Waves or EM waves. The concept of EM waves can also be understood by visualizing the waves in which there are sinusoidal variations of vectors of the magnetic and electric field which are perpendicular to each other and also at right angles to the wave propagation direction.

Unit 5 - Electromagnetic Waves along with Unit 6 - Optics has a weightage of 18 marks in the CBSE Class 12 Physics Examination. The NCERT Solutions for Class 12 Physics Chapter 8 covers concepts of displacement current, electromagnetic spectrum, Maxwell Equations, etc.

Download PDF: NCERT Solutions for Class 12 Physics Chapter 8


NCERT Solutions for Class 12 Physics Chapter 8

The NCERT solutions for class 12 physics chapter 8: Electromagnetic waves are given below:

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CBSE Class 12 Physics Chapter 8 Important Topics

  • Electromagnetic Waves are the waves produced when an electric field comes in contact with a magnetic field.

The direction of the propagation of EM waves is given by a vector cross product of the electric and magnetic fields as

\(\overrightarrow E \times \overrightarrow B\)

  • Equation of Speed of EM Wave: The relation between the speed of light, permittivity constant, and permeability constant is as follows:
\(c = {1 \over \mu_0 \epsilon_0}\)
  • The wavelength for the various spectrum of light is as follows - 
    • Radio Waves > 0.1 m
    • Microwave - 0.1m to 1 mm
    • Infrared waves - 1 mm to 700 nm
    • Visible light - 700 nm to 400 nm
    • Ultraviolet - 400 nm to 1nm
    • X-rays - 1nm to 10-3 nm
    • Gamma rays < 10-3 nm

According to their wavelength or frequency, EM waves can be classified as Electromagnetic Spectrum that ranges from 400 nm to 700 nm.

  • Applications of Electromagnetic Waves: Electromagnetic Waves play an important role in communication technology.
The infrared radiations are used in the security cameras for night vision. UV rays can be helped to detect forged banknotes.

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CBSE CLASS XII Related Questions

  • 1.
    Assertion : Photoelectric effect is a spontaneous phenomenon. Reason (R): According to the wave picture of radiation, an electron would take hours/days to absorb sufficient energy to overcome the work function and come out from a metal surface.

      • 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.

    • 2.
      Assertion : Induced emf produced in a coil will be more when the magnetic flux linked with the coil is more. Reason (R): Induced emf produced is directly proportional to the magnetic flux.

        • 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.

        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.

        • 4.
          Nuclides with the same number of neutrons are called:

            • Isobars
            • Isotones
            • Isotopes
            • Isomers

          • 5.
            A square loop of side 0.50 m is placed in a uniform magnetic field of 0.4 T perpendicular to the plane of the loop. The loop is rotated through an angle of 60° in 0.2 s. The value of emf induced in the loop will be:

              • 5 V
              • 3.5 V
              • 2.5 V
              • Zero V

            • 6.
              A part of a wire carrying \( 2.0 \, \text{A} \) current and bent at \( 90^\circ \) at two points is placed in a region of uniform magnetic field \( \vec{B} = -0.50 \, \hat{k} \, \text{T} \), as shown in the figure. Calculate the magnitude of the net force acting on the wire.

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