Class 12 Physics — Chapter 8: ELECTROMAGNETIC WAVES

What you'll learn

• ▸Displacement Current and Ampere-Maxwell Law
• ▸Maxwell's Equations
• ▸Sources of Electromagnetic Waves
• ▸Nature and Properties of Electromagnetic Waves
• ▸Electromagnetic Spectrum
• ▸Hertz's Experiment

Chapter Summary

--- PAGE 1 --- Chapter Eight ELECTROMAGNETIC WAVES 8.1 INTRODUCTION In Chapter 4, we learnt that an electric current produces magnetic field and that two current-carrying wires exert a magnetic force on each other. Further, in Chapter 6, we have seen that a magnetic field changing with time gives rise to an electric field. Is the converse also true? Does an electric field changing with time give rise to a magnetic field? James Clerk Maxwell (1831-1879), argued that this was indeed the case – not only an electric current but also a time-varying electric field generates magnetic field. While applying the Ampere’s circuital law to find magnetic field at a point outside a capacitor connected to a time-varying current, Maxwell noticed an inconsistency in the Ampere’s circuital law. He suggested the existence of an additional current, called by him, the displacement current to remove this inconsistency. Maxwell formulated a set of equations involving electric and magnetic fields, and their…

Practice Questions from this Chapter

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1. Explain how radio waves travel. Get Solution →
2. Describe what makes light a wave. Get Solution →
3. Illustrate displacement current's purpose. Get Solution →
4. Who first argued that a time-varying electric field generates a magnetic field, leading to the concept of displacement current? Get Solution →
5. What is the fundamental source of electromagnetic waves according to Maxwell's theory? Get Solution →
6. In an electromagnetic wave, what is the orientation of the electric field, magnetic field, and the direction of propagation? Get Solution →
7. Who experimentally demonstrated the existence of electromagnetic waves in 1885? Get Solution →
8. What remarkable conclusion did Maxwell's work lead to regarding the nature of light? Get Solution →

Did you know?

• 💡 Light from the sun takes about eight minutes to travel to Earth.
• 💡 Your eyes can only see a tiny sliver of all electromagnetic waves.
• 💡 James Maxwell showed electricity, magnetism, and light are truly connected.
• 💡 Microwave ovens use electromagnetic waves to quickly heat your food.
• 💡 Many remote controls use infrared electromagnetic waves to change channels.

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