CLASS 12 ASSIGNMENT 6 ELECTROMAGNETIC WAVES

 CLASS 12 

ASSIGNMENT 6

ELECTROMAGNETIC WAVES


1. What is displacement current?


2. State the important consequences of displacement current.


3. Discuss the inconsistency in Ampere's circuital law.  What modification was made by Maxwell in this law?


4. What is displacement current due to?


5. Is the steady electric current the only source of magnetic field? Justify your answer.


6. Distinguish between displacement current and conduction current.


7. Write down Maxwell's equations for steady electric field.


8. Write down Maxwell's equations for steady magnetic field.


9. What are electromagnetic waves?


10.  Do electromagnetic waves carry energy and momentum?


11. Name the basic source of electromagnetic waves.


12. The charging current for a capacitor is 0.25 A. What is the displacement current across its plates?


13.  Give an example to show how e.m. waves carry energy and momentum.


14. How are electromagnetic waves produced?


15. Show that e.m. waves are transverse in nature.


16. What is intensity of an e.m. wave?  Obtain an expression for it.


17. Explain how an accelerating charge acts as a source of e.m. waves.


18. How were the various properties of e.m. waves demonstrated by Hertz?


19. Give a brief history of the observation of electromagnetic waves.


20. Prove mathematically that e.m. waves are transverse in nature.


21. Write an expression for 

(i) momentum carried by an e.m. wave.

(ii) pressure exerted by an e.m. wave.


22. Mention the various properties of e.m. waves.


23. The amplitude of the magnetic field part of a harmonic e.m. wave in vacuum is Bₒ =510 nT. What is the amplitude of the electric field part of the wave?


24. A plane electromagnetic wave travels in vacuum along Z direction.  What will be the direction of the electric and magnetic field vectors?  If the frequency of the wave is 30 MHz, what is its wavelength?


25. Name the scientist who

(i) first predicted the existence of e.m. waves

(ii) first produced e.m. waves

(iii) first set up the transmitter and receiver of e.m.  waves.


26.  On what factors does the velocity of an e.m. wave in vacuum depend?


27. Explain why sound is not electromagnetic in nature.


28. What feature of e.m. waves led Maxwell to conclude that light itself is an e.m. wave?


29. What is electromagnetic spectrum?


30. What is greenhouse effect?


31. Name the e.m. waves which are used 

(i)   in water purification

(ii)   in eye surgery

(iii)  as a diagnostic tool for surgery

(iv)  in treatment of cancer tumours

(v)   in telecommunication

(vi)  to maintain earth's warmth


32. Name the e.m. waves

(i) having maximum frequency

(ii) having minimum frequency


 33. Suppose that the electric field part of an electromagnetic wave in vacuum is E = {(3.1 N/C) cos [(1.8 rad/m) y + (5.4 × 106 rad/s)t]} ˆi .

(a) What is the direction of propagation?


(b) What is the wavelength λ?


(c) What is the frequency ν?


(d) What is the amplitude of the magnetic field part of the wave?


(e) Write an expression for the magnetic field part of the wave.


34. What is the frequency range of the e.m. waves used for studying crystal structure of solids.


35. What is the importance of ozone layer in the atmosphere?


36. Name the different layers of the earth's atmosphere.


37. Give one example each to illustrate the situation where there is

(i) displacement current but no conduction current and 

(ii) only conduction current but no displacement current.


38. In a plane electromagnetic wave, the electric field oscillates sinusoidally at a

 frequency of 2.0 × 10¹⁰ Hz and amplitude 48 V/m 

(a) What is the wavelength of the wave?


(b) What is the amplitude of the oscillating magnetic field?


(c) Show that the average energy density of the Electric field equals the average energy density of the Magnetic field.  ( c = 3\times 10^{8}\;m\;s^{-1} )



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