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.
    Differentiate between inductive reactance, capacitive reactance and impedance of an ac circuit.
    An ideal inductor and an ideal capacitor are connected in series across an ac voltage. Plot a graph showing variation of net reactance of the circuit with frequency of the applied ac voltage.


      • 2.
        Two small identical metallic balls having charges \( q \) and \( -2q \) are kept far at a separation \( r \). They are brought in contact and then separated at distance \( \frac{r}{2} \). Compared to the initial force \( F \), they will now:

          • attract with a force \( \frac{F}{2} \)
          • repel with a force \( \frac{F}{2} \)
          • repel with a force \( F \)
          • attract with a force \( F \)

        • 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 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:

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

            • 5.
              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.


                • 6.
                  A ray of light MN is incident normally on the face corresponding with side AB of a prism with an isosceles right-angled triangular base ABC. Trace the path of the ray as it passes through the prism when the refractive index of the prism material is \( \sqrt{2} \), and \( \sqrt{3} \).

                    CBSE CLASS XII Previous Year Papers

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