CBSE Class 12 Physics Electromagnetic Waves Notes Set C

Download CBSE Class 12 Physics Electromagnetic Waves Notes Set C in PDF format. All Revision notes for Class 12 Physics have been designed as per the latest syllabus and updated chapters given in your textbook for Physics in Class 12. Our teachers have designed these concept notes for the benefit of Class 12 students. You should use these chapter wise notes for revision on daily basis. These study notes can also be used for learning each chapter and its important and difficult topics or revision just before your exams to help you get better scores in upcoming examinations, You can also use Printable notes for Class 12 Physics for faster revision of difficult topics and get higher rank. After reading these notes also refer to MCQ questions for Class 12 Physics given on studiestoday

Revision Notes for Class 12 Physics Chapter 8 Electromagnetic Waves

Class 12 Physics students should refer to the following concepts and notes for Chapter 8 Electromagnetic Waves in Class 12. These exam notes for Class 12 Physics will be very useful for upcoming class tests and examinations and help you to score good marks

Chapter 8 Electromagnetic Waves Notes Class 12 Physics

 Ch: Electromagnetic Waves

Class XII Physics

Chapter Notes

Top Concepts

1. Displacement current is due to time-varying electric field and is given by

 i=EΦ E /dt

Displacement current acts as a source of magnetic field in exactly the same way as conduction current.

2. Electromagnetic waves are produced only by charges that are accelerating, since acceleration is absolute, and not a relative phenomenon. An electric charge oscillating harmonically with frequency , produces electromagnetic waves of the same frequency v. An electric dipole is a basic source of electromagnetic waves.

3. Electromagnetic waves with wavelength of the order of a few metres were first produced and detected in the laboratory by Hertz in 1887. He thus verified a basic prediction of Maxwell’s equations.

4. Electric and magnetic fields oscillate sinusoidally in space and time in an electromagnetic wave. The oscillating electric and magnetic fields, E and B are perpendicular to each other, and to the direction of propagation of the electromagnetic wave.

 class_12_physics_concept_4

 6. The speed c of electromagnetic wave in vacuum is related to 0 and 0 (the free space permeability and permittivity constants) as follows:

 c =1/ √μoεo

The value of c equals the speed of light obtained from optical measurements. Light is an electromagnetic wave; c is, therefore, also the speed of light. Electromagnetic waves other than light also have the same velocity c in free space.

The speed of light, or of electromagnetic waves in a material medium is given by  v 1/ √με

where μ is the permeability of the medium and ε its permittivity.

7. Electromagnetic waves carry energy as they travel through space and this energy is shared equally by the electric and magnetic fields.

8. If in a region of space in which there exist electric and magnetic fields , there exists Energy Density (Energy per unit volume) associated with these fields given by and E and B

   class_12_physics_concept_5(0.1)

where we are assuming that the concerned space consists of vacuum only.

9. Electromagnetic waves transport momentum as well. When these waves strike a surface, a pressure is exerted on the surface. If total energy transferred to a surface in time t is U, total momentum delivered to this surface is p = U/c.

10. The spectrum of electromagnetic waves stretches, in principle, over an infinite range of wavelengths. The classification of electromagnetic waves according to frequency is the electromagnetic spectrum. There is no sharp division between one kind of wave and the next. The classification has more to do with the way these waves are produced and detected. Different regions are known by different names; Υ-rays, X-rays, ultraviolet rays, visible rays, infrared rays, microwaves and radio waves in order of increasing wavelength from 10-2 Å or 10-12 m to 106 m.

CBSE Class 12 Physics Notes - Electromagnetic Waves

11.
(a) Radio Waves: Produced by accelerated motion of charges in wires. They are used in radio and television communication systems. They are generally in the frequency range from 500 kHz to about 1000 MHz.

(b) Microwaves: These are short wavelength radio waves with frequencies in the gigahertz range. Due to their short wavelengths, they are suitable for radar systems used in aircraft navigation. Microwave ovens use them for cooking.

(c) Infrared Waves: These are produced by hot bodies and molecules. They lie in the low frequency or long wavelength end of the visible spectrum.

(d) Visible Light: The spectrum runs from about 4x1014Hz to about 7x1014Hz . Our eyes are sensitive to this range of wavelengths.

(e) Ultraviolet light: It covers wavelengths ranging from 400 nm to 0.6 nm. The sun is an important source of UV rays.

(f) X-rays: These cover the range 10 nm to about10-4 nm.

(g) Gamma Rays: These lie in the upper frequency range of the spectrum, and have wavelengths in the range 10 -10 - 10 -14 m.

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CBSE Class 12 Physics Chapter 8 Electromagnetic Waves Notes

We hope you liked the above notes for topic Chapter 8 Electromagnetic Waves which has been designed as per the latest syllabus for Class 12 Physics released by CBSE. Students of Class 12 should download and practice the above notes for Class 12 Physics regularly. All revision notes have been designed for Physics by referring to the most important topics which the students should learn to get better marks in examinations. Our team of expert teachers have referred to the NCERT book for Class 12 Physics to design the Physics Class 12 notes. After reading the notes which have been developed as per the latest books also refer to the NCERT solutions for Class 12 Physics provided by our teachers. We have also provided a lot of MCQ questions for Class 12 Physics in the notes so that you can learn the concepts and also solve questions relating to the topics. We have also provided a lot of Worksheets for Class 12 Physics which you can use to further make yourself stronger in Physics.

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