 I like to teach people,my favourite subject  physics and math.I enjoy cricket ,tour

Rajesh Kumar

In this course, the educator discusses the nature of light waves, historical background, detailed Mathematical analysis, properties of light waves, principal of reflection and refraction of light waves, diffraction,  polarisation etc.

Ace in Class XI Examination by understanding all the concepts of Mathematics and Science, with these courses.

CBSE Class 11

Hindi

(Hindi) Light Wave: Class 11 NCERT

Waves

Oscillation & Waves

Physics

Class 6-12

Become a topper in your school and ace your board exams by learning from best educators in the country

CBSE

CBSE (Central Board of Secondary Education)

Course overview of light wave.  List of topic covers in this course.

Light wave:Course Overview (in Hindi)

Historical background for light as a wave or a particle. From newtons,  hygens priciple, fresnel,  young double slit, hertz to Albert Einstein.

Light:Wave or Particle (in Hindi)

Wave is of two types mechanical and non mechanical light wave is non mechanical wave it doesn't require any material medium light wave mainly created by electric field and magnetic field so this is called electromagnetic wave speed of light wave is a Universal constant which is denoted by capital c is equal to 3 multiply 10 to the power 8 metre per second with respect to any object that is the basis of special theory of relativity.

The Nature of Light Wave Part :01 (in Hindi)

Colour of light visible to human eye. Relation between frequency and wavelength. Geometrical optics aproximation. Light rays.

The Nature of Light Wave Part:02 (in Hindi)

Huygens principle : 
Proposer of the wave theory of light . he considered light is a mechanical wave moving in a hypothetical medium known as Ether.  hygens principle : various points of an orbital surface when reached by a wavefront become secondary sources of light emitting secondary wavelets the disturbance beyond the surface results from the superposition of these secondary wavelets . hygens construction:  The geometrical envelope of secondary wavelets at any given later instant represents the new position of the wavefront at that instant it is valid for light waves.  the surface used in the hygens construction may have any arbitrary shape. if medium is homogenous light moves forward and does not reflect back .  if change in medium the wave maybe reflected from the discontinuity then secondary wavelets on the backside should also be considered . reflection of light:  here AB is equal to the Wavefront of the incident light at time t is equal to zero .Sigma is equal to source of secondary wavelets V is equal to speed of light . incident ray perpendicular to a b and the normal is perpendicular to AC angle A is equal to angle BAC and angle R is equal to angle ACD.  triangle ADC congruent triangle ABC. therefore angle BAC is equal to angle DCA this implies angle A is equal to angle r that is angle of incidence is equal to angle of reflection . incident ray ,reflected ray and normal all are in same plane that is coplanar which proof the reflection of light by hygens principle .  refraction of light:  a b is equal to incidentvwavefront CD is equal to secondary wavefront .sini  is equal to bc by ac is equal to V1t divided by AC , sinr  is equal V2t by AC,   comparing this We get sin i / sinr is equal to V1 upon V2 that is known as snell’s law here V1 and V2 are speed of light in medium 1 and medium 2, the ratio of V1 and V2 known as refractive index of medium 2 with respect to medium 1 which is represented by Mu of 21 . if medium one is vacuum then mewtwo 1 is equal to move refractive index of medium to YouTube one is written in another format beauty divided by new one incident ray reflected ray and normal all are in same plane that is coplanar which proves the law of refraction of light by hygens principle. if medium one is a medium to is better than angle A is equal greater than angle R that is even greater than B to this is opposite to the prediction of the Newton’s corpuscular theory Newton says that when medium change then denser medium attract light particle that is denser medium speed of light is Greater.

Huygens Principle (in Hindi)

Young double slit experiments. Thomas young in 1801 reported his experiment on the interference of light. young double hole experiment one of them two waves interfered to give a pattern of bright and dark areas . the variation of intensity on the screen shows the interference taking place between the light waves reaching the screen from the two pin pinholes. if light of single wavelength used then pattern of bright and dark areas are sharply defined . in young double slit experiment S1 and S2 these are two long parallel slits , source is parallel beam of monochromatic light . we have to calculate electric field at point P on the screen due to two waves. and finally we calculate the resultant of two electric field at point P. then we calculate phase difference between these two electromagnetic waves arriving at B. phase difference phase (¢)  is equal to 2pi by Lambda in to path difference (∆x). the resultant field at point P is calculated by in the form of resultant vector for first vector is electric field amplitude E1, electric field amplitude E2 and resultant electric field isE०, for bright fringe constructive interference for the phase difference is equal to 2 Pi ,in other form path difference Delta x is equal to n Lambda ,for dark fringe of destructive interference phase difference is equal to( 2 n + 1 )Pie   or Delta x is equal to (N + half )Lambda. at the centre of the screen bright fringe ,for  n is equal to zero .how we can calculate intensity variation if amplitude of both electric wave or  electric field   E 1 and E 2 , equal to E0' . then resultant amplitude is  square of E0' (1 + cos Lambda ). intensity is directly proportional to the square of the amplitude . so intensity I is equal to 2 I in to ( oneplus cause delta) or equal to 4I cos square Delta by2. the resultant intensity at centre Delta equal to zero so be on maximum intensity at centre for bright fringe . and for dark fringe phase difference (2n+ pi). intensity for dark fringe is equal to zero . so on the screen intensity of the fringe, vary from 0 to 4I'. fringe width separation between two consecutive bright or dark fringe is known as fringe width separation between the slits small d and between slit and a screen is capital D if capital D very very greater than a small D then path difference Delta x is equal to small d multiply sin theta that theta is the angle between slit to the centre of the screen line and centre of the slit to point P . that is POB is equal to theta. which is also equal to S1 S2 is equal to theta then path difference Delta is equal to  dsin theta , theta is very small. so we can also write in approximation deltax is equal to tan theta the whole Delta x is equal to a small D into by divided by capital D for bright fringe Delta x is equal to nLambda ,is equal to small d sintheta . Capital D there  to in capital D Lambda divided by small D that is at both side of the centre in upward and downward direction. both side on Plus and minus side of centre of the screen so bar. if d  between the slit increases ringe width  decreases , if slit between distance between slit is very very greater than D then fringewidth is  small, very very less than one that is very very less than 1  then maxima and minima so in general difficult to observe.

(Hindi) Young double slit experiment

Optical path is equal to multiplication of geometrical path and refractive index of medium in which light travel.
When refractive index close to Unity then geometrical path is equal to optical path . when light goes from vacuum to new medium then frequency of the light wave not changed , frequency always depends on source. on same wavefront phase of different particles has a constant value. phase of light wave change by equal amount whether it covers a distance BC is equal to miyuAD in vacuum or AD in the medium then miyu IAD is known as optical path . hear a b a c e and a d e are different but the optical parts are equal ..the ray having longer geometrical path covers less distance in the lens as compared to the ray having shorter geometrical path.

(Hindi)Optical path

Interference due to thin film. 
Parallel beam of light is incident on the film at an angle i as shown in figure. the wave is divided into two parts at the upper surface one is reflected and the other is refracted. This part divided into two parts one is transmitted out of the film and the other is reflected back. multiple reflection and refraction take place and a number of reflected waves as well as transmitted waves are sent by the film, the film may be viewed by the reflected light or by the transmitted light. in the case of transmitted light for normal incidence i is  equal to zero. point B and D coincide, path BP is equal to DP and the only difference is the distance travelled by the wave DP is bc + CD is equal to 2 d. optical path difference between waves BP and DP interfering it is Δx=2µd,the same phase difference by the DP and SP or any consecutively transmitted waves. all these waves are in phase if phase difference  ΔΦ=2nπ . n is Integer and 2µd=nλ. then constructive interference take place and the film is seen illuminated . and if Δx=2µd is  equal to phase difference to ΔΦ=(2n+1)π and 2µd=(n+1/2)λ, consecutive waves are out of phase the illumination will be comparatively less because of interfering waves do not have equal magnitude. if white light used for constructive interference for certain wavelength and which colour will be strongly transmitted . in the case of destructive interference poorly transmitted gives coloured appearance of the film. in the case of reflected wave when we used again the optical path difference between the reflected consecutive waves is equal to  Δx=2µd in the case of reflection, illumination minimum  in reflection  maximum and minimum condition in reflection case is just opposite that of the transmission case. because light goes from rarer to denser medium then in the case of reflection a sudden change of phase of 2nd wave by π.

(Hindi)Interference from thin film

Interference pattern and experiment by Fresnel Biprism. Demonstrated the phenomenon of interference between two coherent light beams. used single monochromatic light , also used to find the wavelength of the given light source. Biprism used for producing two coherent sources from a single source ,thin prism joined at the base to form  Biprism, base angle of prism is very small .refracting angle is equal to 0.5 degree. monochromatic light placed parallel to the refracting edge. S1and S2 are the virtual image of source , is as formed by the prism A1BC and A2BC interference fringe formed on the  screen .fringe width obtained on the screen is beta =Dλ/d as in   young double slit experiment. 
:coherent and incoherent sources: 
Wave1 and wave 2 has initial phase difference Delta zero, remains constant in time then these are called coherent sources. if Delta zero changed randomly with respect to time known as incoherent. for producing interference pattern source must be coherent light emitted by atom in discrete steps for short time it become actived then inactive for 10 to the power minus 8 second .inactive condition wavetrain of several metres.  path difference must be in centimetres for good interference pattern on screen. strictly monochromatic means well defined single frequency or wavelength must be a sine wave which has infinite extension. ordinary sodium vapour lamp has wavelength 589.00 NM and 589.6 NM . Spread in wavelength is approx plus minus 0.01 NM . the length of the wave train larger then  spread in wavelength smaller .wavelength should be several hundred meter  for good interference pattern. laser source is a good source of monochromatic . for laser source behave in a Cooperative manner. hence light is coherent. 
two independent laser sources can produce interference fringes.

(Hindi)Fresnel Biprism

Diffraction of light: the bending of light wave around  opening or an obstacle is known as diffraction of light .when light passes through a slit then opening of The slit  through which  light wave passes then particles between opening behave as secondary wavelets, this wavelets now behave as a source of light wave and these waves interfere at screen. where interference pattern of maxima and minima found this pattern is known as fringe. and this phenomenon is known as diffraction of light .distance between slit and screen is infinite and source of light and difracting  element also distance is in Infinity then that special case known as 'fraunhofer diffraction' and when these distance in a finite measurements then that diffraction is known as 'fresnel diffraction. here we discuss about fraunhofer diffraction, width of opening b ,A converging lens and a screen screen is at focus of the converging lens and light waves which come out of opening is now parallels interfere at screen.at p0 on screen Central Maxima at  θ=  0,waves from the portion b/2 of opening ,then path difference between waves coming from this opening  is Δx = b/2sinθ if path difference is  λ /2, then phase difference between these waves is π. that is the Waves from upper half of the opening  is out of phase from lower half of opening.  at point P the interference patterns cancel out each other and be observed minimum intensity.   maximum intensity found between to minimum intensity .that is for diffraction of light ,opening/ obstacle must be comparable in dimension with respect to wavelength of light.

(Hindi)Diffraction of light: Fraunhofer Diffraction

Fraunhofer diffraction by circular aperture and Fresnel diffraction at a sharp edges. Lens never makes point image of distant point source. Image disc made by converging lens.  Radius of image disc calculated.radius of  1st dark fringe circular disc calculated. Light diffraction at edge of Door or window happens in daily life. Diffraction from clouds.

(Hindi) fraunhofer diffraction by circular aperture,Fresnel diffraction at a straight Edge

Limit of resolution,  Rayleigh criteria and law of scattering by rayleigh. Example of scattering of sunlight.

(Hindi) Limit of resolution, Scattering of Light,Rayleigh Criterion/ Law

Polarisation of light: directions of electric field perpendicular to the directions of wave.magnitude varying sinusoidally with space and time. perpendicular to X -axis there are infinite directions possible in y ,Z and y- z plane.If the electric field at the point always remains parallel to a fixed direction as the time passes the light is called linearly polarized along that direction. the plane containing the electric field and the directions of propagation of wave is called the plane of polarization. the resultant electric field at a point keeps on changing its direction randomly and rapidly is known as unpolarised light. the light emitted by electric lamp a candle, sun is the best example. if phase difference between y component and Z component of electric field varies with time then light is unpolarized . if phase difference is equal to zero then electric field always parallel to fixed direction ,that is linearly polarized . if phase difference is equal to π  then resultant electric field again  parallel to a fixed direction and light is linear polarization. difference between Y and Z component of electric field is equal to 90 degree or π/2 and Y and Z component of electric field have equal magnitude, then angle θ becomes( ωt-  kx ) then at any point θ increases at a uniform rate ω and resultant field becomes equal to E1or  E2 then magnitude of the field remains constant . the tip of the electric field does goes in a circle at a uniform angular speed the light is called a circularly polarized light . If phase difference between y and z component of electric field π/2 but E1not equal to E2 then the tip of the electric field goes in  an ellipse then light is electrically elliptically polarised light.

(Hindi) Polarization of light

Polaroids,Polarization by reflection and refraction,Polarization by Scattering. 

Polaroids method by which unpolarised light converted into polarised light, instrument used known as polarizer .plane seat of circular shape known as disc also known as polaroids. polaroids transmit light, electric field vector parallel to special direction in the sheet .polaroids consists of long Chains of hydrocarbons ,conducting at optical frequency .light falls perpendicular on the sheet and electric field parallel to chain ,which absorbed electric current in the chain. when light perpendicular to chain gets transmitted to transmission axis of the polaroid. when light passes through the polaroid the transmitted light becomes linearly polarized with electric vector parallel to the transmission Axis. when E- vector parallel to T- axis then completely transmitted by the polaroid and when perpendicular then completely stopped . when a vector is at angle theta with TAxis then partially transmitted the intensity of light is I is equal to I° cos squared theta ,known as law of malus. I° is the intensity when the incident E vector is parallel to the Taxis . polarization by reflection and refraction : incident, reflected and refracted ray all are in one plane plane of incidence here is xy plane . when  arrow size reduced and dot same size then reflection in xy plane ,electric component . when Arrow same size and the dog reduced in refracted case. If tani= μ ,reflected light is completely polarized with electric field in Z direction .refracted light never completely polarized. the angle i called Brewster angle ,then known as brewster's law . reflected light is polarised used in preparing sunglasses which reduce the glare from roads, snow, water surfaces. Sun glasses are polaroids . TAxis perpendicular to the director of the polarized reflected light. which is responsible for the Glare is the largely absorbed. ordinary dark coloured sunglasses which absorb any light passing through them which reduce the intensity to a large extent. polarisation by scattering unpolarised light scattered by small particles light is partially polarised. the blue light received from the sky is partially polarized . human eye does not distinguish between an unpolarized light and polarised light. the eyes of a bee can detect the difference. also can determine the direction of polarization

Polaroids, Polarization by reflection and refraction Polarization by Scattering

Summary of light wave, refractive index, phase difference ,young double slit experiment, fringe width ,fresnel biprism, directions wavelength of light and wave front.

(Hindi) summary light waves-01

(Hindi) summary of light wave - 02

Numerical based on wave nature of light, young double slit experiment, single slit diffraction and polarization based question and answer. IITJEE2018 PREVIOUS YEARS QUESTIONS.

Numerical based on light waves

Through Unacademy , want to reach out to students...those who really needs me.
Trying to help how to learn basics with simple tricks .

Susmita Mahapatra

This course discusses CBSE Class 11 Science topic on Waves - Types of Waves, Equation of Plane progressive waves, Energy transmission in waves, Laws of Transverse vibration, Newton's formula for sound in air and Laplace correction, Reflection of Waves, Superposition of Waves and Stationary Waves.

CBSE Class 11 - Waves

State topper in school exams, selected in IIT Kharagpur, M.Sc., 30 yrs in teaching.

Pradeep Kshetrapal

Different concepts and equations of oscillations are explained with help of questions asked in previous NEET examinations.

NEET 4 Oscillations

wave motion and waves on a string, equation of traveling wave, velocity of a wave on a string, interference and the principle of superposition, reflection and transmission of waves, standing wave, laws of transverse vibrations of a string: sonometer, transverse and longitudinal waves, polarization of waves.

(Hindi) Wave Motion In One Direction

Rahul Mandal

This course will help you to understand the Nature of Electromagnetic waves or radiation.  And all the topics which are related to this course are explained in so simple and easiest method with deep understanding i.e. Introduction of EMW,  properties of Electromagnetic waves or radiation, visible spectrum for EMW radiation regions and also some importants Numericals based on this theory.  And guys don't worry those all topics are explained in basic terms.  So if you like my lessons then do RATE, REVIEWS AND RECOMMEND to this course and don't forget to follow me for lettest updates regarding to this course.  Thank you

Lessons

17 lessons • 2h 53m

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Light wave:Course Overview (in Hindi)

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Light:Wave or Particle (in Hindi)

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The Nature of Light Wave Part :01 (in Hindi)

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The Nature of Light Wave Part:02 (in Hindi)

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Huygens Principle (in Hindi)

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(Hindi) Young double slit experiment

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(Hindi)Optical path

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(Hindi)Interference from thin film

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(Hindi)Fresnel Biprism

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(Hindi)Diffraction of light: Fraunhofer Diffraction

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