Why electromagnetic waves travel v2
Download as PPTX, PDF
2 likes106 views
Understand Electromagnetism with Timelines of Discovery Electromagnetism Theories and Equations in Discovered Understand Electromagnetic Waves Why Electromagnetic Waves Move and are Traversal Waves
Why electromagnetic waves travel v2
- 1. Deep Science in Brief Aims: Understand Electromagnetism with Timelines of Discovery Electromagnetism Theories and Equations in Brief Understand Electromagnetic Waves Why Electromagnetic Waves Move and are Traversal Waves Why Electromagnetic Waves are Traversal Waves Nalaka Dissanayake, Electronic and Telecommunication Engineer, Senior Lecturer
- 2. Deep Science in BriefDeep Science in Brief Nalaka Dissanayake, Electronic and Telecommunication Engineer, Senior Lecturer Focus Point: Why Electromagnetic Waves are Traversal Waves What are EM Waves Oscillating electric and magnetic fields perpendicular to each and propagates 1887, Heinrich Rudolf Hertz, German physicist, first to generate electromagnetic waves in a laboratory
- 3. Deep Science in BriefDeep Science in Brief Nalaka Dissanayake, Electronic and Telecommunication Engineer, Senior Lecturer Brief Illustration of Electromagnetism Using Physics 1785, Coulombs law and Gauss laws: There is a force due to a charge resulting an electric filed around the charge +q 2 o q E = 4 r逸 r Focus Point: Why Electromagnetic Waves are Traversal Waves
- 4. Deep Science in BriefDeep Science in Brief Nalaka Dissanayake, Electronic and Telecommunication Engineer, Senior Lecturer Brief Illustration of Electromagnetism Using Physics 1819, Right hand Thumb Rule: Hans Cristian Oersted, French Physician, demonstrated when a currents flows thru a wire there is a magnetic filed around it r Focus Point: Why Electromagnetic Waves are Traversal Waves
- 5. Deep Science in BriefDeep Science in Brief Nalaka Dissanayake, Electronic and Telecommunication Engineer, Senior Lecturer Brief Illustration of Electromagnetism Using Physics 1831, Faraday's Law of Induction Faraday, England chemist, discovered that a change in magnetic filed causes a change in electric filed. r Focus Point: Why Electromagnetic Waves are Traversal Waves
- 6. Deep Science in BriefDeep Science in Brief Nalaka Dissanayake, Electronic and Telecommunication Engineer, Senior Lecturer Brief Illustration of Electromagnetism Using Physics 1887, Heinrich Rudolf Hertz, German physicist, first to generate electromagnetic waves in a laboratory In 1895, Italian electrical engineer Marconi invented to send messages over long distances using radio waves Focus Point: Why Electromagnetic Waves are Traversal Waves 1873, Maxwel created equations for all above electromagnetism phenomena
- 7. Deep Science in BriefDeep Science in Brief Nalaka Dissanayake, Electronic and Telecommunication Engineer, Senior Lecturer Detailed Illustration: Why Electromagnetic Waves are Traversal Waves Electromagnetic Radiation by an Object or an Antenna Only an accelerated electric charge forms a strong electric field component perpendicular to the radial electric filed lines, even at far from charge which leads to EM radiation vv.t r 慮 慮 None of above theories illustrate why EM waves travel and radiate In 1907, Thomson demonstrated a mathematical model to understand
- 8. Deep Science in BriefDeep Science in Brief Nalaka Dissanayake, Electronic and Telecommunication Engineer, Senior Lecturer Detailed Illustration: Why Electromagnetic Waves are Traversal Waves Illustration, in 1907 J.J. Thomson: When electrons move (accelerate) a very small time, a new set of electric filed lines are formed. But still the electric filed lines at far havent received the information on the charges acceleration (New position) and are centered to the old charge position. Since lines have to be contagious (Gausss Law), transition of new filed lines to old field lines should happen, but are not parallel to the radial direction (There is some angle) Therefore in the transition component of the electric filed, there is some component of the electric filed, at the perpendicular direction to the radial lines and also are very high strength (Proved with mathematics) This perpendicular component of the impulse electric field pulse leads to EM radiation forming the EM wave vv.t r 慮
- 9. Deep Science in BriefDeep Science in Brief Nalaka Dissanayake, Electronic and Telecommunication Engineer, Senior Lecturer Mathematical Model: Why Electromagnetic Waves are Traversal Waves At time t=o electron is at origin. We consider the electric filed at a distance r-=ct (c=velocity of light) and r>> v. t Charge is accelerated right a t very small time to reach v small velocity (a= v/ t) As per Gausss low, Electric filed strength of charge q at r distance, = = ヰ.. .ヰ = 乞. ヰ. . . ヰ = 4 2 . ヰ. . . ヰ = . 1 4 . ヰ ヰ . . 1 2 . = c. t = . . . 咋 v v.t r 慮 慮
- 10. Deep Science in BriefDeep Science in Brief Nalaka Dissanayake, Electronic and Telecommunication Engineer, Senior Lecturer Mathematical Proof: Why Electromagnetic Waves are Traversal Waves = . . . 咋 Thus, an accelerating electron produces pulse of EM radiation at right angles to the direction of radial electric field .. Even at the far from the sources, the radiative fields will be very stronger as per the equation It depends on 1/r and not 1/r2. Larger the acceleration the greater the EM pulse.