propagation of electromagnetic waves class 12

Free PDF Download of CBSE Physics Multiple Choice Questions for Class 12 with Answers Chapter 8 Electromagnetic Waves. Faraday's Law of Electromagnetic Induction, \varepsilon = - {{d{\Phi _B}} \over {dt}}  or  \oint {\vec E.d\vec l = - {{d{\Phi _B}} \over {dt}}}, \oint {\vec B.d\vec l} = {\mu _o}\left( {{I_C} + {\varepsilon _o}{{d{\Phi _E}} \over {dt}}} \right). It also bends around the corner of the objects on the earth, Due to this, the energy of the ground wave is gradually absorbed by the earth and the power of the ground wave decreases, The power of the ground wave decreases with the increase in the distance from the transmitting station. This phenomenon of loss of power of the ground wave is called attenuation, The attenuation of ground waves increases very rapidly with the increase in its frequency, Thus, ground wave communication is not suited for high frequency signal wave and for very long range communication, To radiate signals with high efficiency, the antennas should have a size comparable to the wavelength of the signal. Video Lesson. The wave equation for light propagating in x-direction in vacuum may be written as, E = {E_o}\sin \omega \left( {t - x/c} \right), where E is the sinusoidally varying electric field at position x at time t. The constant c is the speed of light in vacuum. The four basic laws of electricity and magnetism i.e. (x) Intensity of electromagnetic wave is defined as energy crossing per unit area per unit time perpendicular to the directions of propagation of electromagnetic wave. the electromagnetic waves are radiated out by the transmitter antenna at one place which travel through the space and reach the receiving antenna at the other place. CBSE Class 12 Physics Chapter 8 Electromagnetic Waves notes in PDF are available for free download in myCBSEguide mobile app. Faraday's law of electromagnetic induction states that, \oint {\vec E.d\vec l} = - {{d{\Phi _B}} \over {dt}}    (3). This video will make you understand about the Electromagnetic Waves basic concept. An oscillating charge in an LC circuit also produces EM waves. The generalized form of Ampere's law \oint {B.dl} = {\mu _o}I, which includes both conduction current {I_C} (current flowing through the conducting wire) and displacement current {I_C} as given by Maxwell i.e. Thus I = S The displacement of electrons is caused by the time varying electric field. } (iii) The electric and magnetic field variation are in phase. The ionosphere is also called as thermosphere as temperature increases rapidly here and it is the outermost part of the earth’s atmosphere, Above troposphere, we have various layers like D (part of stratosphere), E (part of stratosphere), F, The ionosphere is called so because of the presence of large number of ions or charged particles. Propagation of Electromagnetic Waves. (b)  The average energy density of magnetic field is, {u_B} = {{{B^2}} \over {2{\mu _o}}} = {{{{\left( {{B_o}/\sqrt 2 } \right)}^2}} \over {2{\mu _o}}} = {{B_o^2} \over {4{\mu _o}}}, (c) {u_E} = {u_B} from y-rays to radio waves. a magnetic field varying with time gives rise to an electric field varying in space. Physics Electromagnetic Waves part 1 (Introduction) CBSE class 12. It is given by 2. Displacement current is that which results due to the displacement of electrons. They do not require a material medium for their propagation. and   {B_Z} = {B_o}\sin \left( {x - ct} \right)     (2) Each electromagnetic wave has its characteristic properties and features. Ionisation occurs due to the absorption of the ultraviolet and other high energy radiation coming from the sun, by the air molecues, The phenomenon of bending of electromagnetic waves in this layer so that they are diverted towards the earth is helpful in skywavepropogation. Accelerated charges are responsible to produce electromagnetic waves. Electromagnetic waves can propagate in vacuum and in a medium. Physics Chemistry Mathematics Biology (b) will have frequency of 2 × 109 Hz. An accelerated charge acts as the source of electromagnetic waves. (iv) EM waves are produced by accelerating charged particle. the electromagnetic waves are radiated out by the transmitter antenna at one place which travel through the space and reach the receiving antenna at the other place. It helps us to categorize various waves based on their frequency, wavelength, uses, and origin. On the receiving end the audio signal is filtered from the carrier waves and this process is known as demodulation. Class 12 Physics Electromagnetic Waves: Nature of EM waves: Nature of EM waves. The signal wave glides over the surface of the earth, While propagating on the surface of the earth, the ground wave induces current in the ground. From equation (1), we have, {{\partial {E_y}} \over {\partial x}} = {E_o}\cos \left( {x - ct} \right), {{\partial {B_y}} \over {\partial t}} = - c{B_o}\cos \left( {x - ct} \right), Substituting for {{\partial {E_y}} \over {\partial x}}  and {{\partial {B_z}} \over {\partial t}}  in equation (1), {E_o} = c{B_o}     or     c = {{{E_o}} \over {{B_o}}}, It shows that the velocity of electromagnetic waves is equal to the ratio of amplitudes of electric and magnetic fields. Therefore, Maxwell modified Ampere’s circuital law. Answer . When energy of electromagnetic wave is incident on a surface, the flux density is called intensity of wave (denoted by I). They do not require any material medium for their propagation. } Zigya App. The modulated signal is sent through transmitting antenna. P = {q^2}{a^2}/(6\pi {\varepsilon _0}{c^3}), where q is the charge on the particle and a is its instantaneous acceleration. Velocity of light, c = 3 x 108 m/s The process by which an audio signal is superimposed over the carrier waves is known as modulation. Zigya App. Notes for Electromagnetic Waves chapter of class 12 physics. These waves required no medium for its propagation. Here, wavelength \lambda = 5.5 x 10-5 cm = 5.5 x 10-7 m At some point by the curvature of the earth, the line of sight propagation gets blocked. Students can solve NCERT Class 12 Physics Electromagnetic Waves MCQs Pdf with Answers to know their preparation level. Propagation of Electromagnetic Waves. (b) These waves propagate through space with speed of light, i.e., 3 10 8 m/s. Figure shows a capacitor made of two circular plates each of radius 12 cm and separated by 5.0 mm. The ionosphere plays a major role in sky wave propagation. They do not require a material medium for their propagation. m = checkTime(m); Properties of elctromagnetic wave (a) ?These waves are transverse in nature and i t does not require a medium for propagation. (d) Total average energy density, {u_E} + {u_B} = 2{u_E} = 2{u_B} = {1 \over 2}{\varepsilon _o}E_o^2 = {1 \over 2}{{B_o^2} \over {{\mu _o}}}, The energy of electromagnetic wave crossing per unit time per unit area perpendicular to the direction of propagation of wave is called the intensity of electromagnetic wave. The intensity of electromagnetic wave is, I = {{{P_{av}}} \over {4\pi {r^2}}} = {u_{av}} \times c = {1 \over 2}{\varepsilon _o}E_o^2c = {1 \over {2{\mu _o}}}B_o^2c = {1 \over {2{\mu _o}}}. var today = day + "-" + month + "-" + now.getFullYear(); 1. The total energy flowing perpendicularly per second per unit area into the surface in free space is called a Poynting vector \vec S, where \vec S = {c^2}{\varepsilon _o}\left( {\vec E \times \vec B} \right) = \left( {\vec E \times \vec B} \right)/{\mu _o}. The threshold frequency for a metallic surface corresponds to an energy of 6.2 eV, and the stopping potential for a radiation incident … Electric field is varying with time, and it will give rise to magnetic field, this magnetic field is varying with time and it gives rise to electric field and the process continues so on. Vacuum and in a vacuum or through a medium d ) fall in the figure.. Physics Notes with proper images & diagram methods in brief propagation gets blocked and! Sinusoidally varying magnetic field associated with electric field when light propagates into play m the region of stratosphere is in. Current Ampere ’ s equations wave is given as: \ ( \vec { E } \vec... 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propagation of electromagnetic waves class 12 2021