This PDF is the Sample PDF taken from our Comprehensive Study Material for NEET & AIIMS

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1 This PDF is the Sample PDF taken from our Comprehensive Stuy Material for NEET & AIIMS To purchase the books, go through the link belowhttp:// ETOOS Comprehensive Stuy Material For NEET & AIIMS

2 CHAPTER 08 WAVE OPTICS A rainbow is the prouct of physics working for your appreciation of beauty. "KYLE HILL" INTRODUCTION P he utch physicist Christiaan Huygens, in 678 put forwar the wave theory of light it is this wave moel of light that we will iscuss in this chpater. As we will see, the wave moel coul satisfactorily explain the phenomena of reflection an refraction; however, it preicte that on refraction if the wave bens towars the normal then the spee of light woul be less in the secon meium. This is in contraiction to the preiction mae by using the corpuscular moel of light. It was much later confirme by experiments where it was shown that the spee of light in water is less than the spee in air confirming the preiction of the wave moel; Foucault carrie out this experiment in 850. The wave theory was not reaily accepte primarily because of Newton's authority an also because light coul travel through vacuum an it was felt that a wave woul always require a meium to propagate from one point to the other. However, when Thomas Young performe his famous interference experiment in 80, it was firmly establishe that light is inee a wave phenomenone. The wavelength of visible light was measure an foun to be extremely small; for example, the wavelength of yellow light is about 0.5 m. Because of the smallness of the wavelength of visible light (in comparison to the imensions of typical mirrors an lenses), light can be assume to approximately travel in straight lines. This is the fiel of geometrical optics, an a ray is efine as the path of energy propagation in the limit of wavelength tening to zero.

3 PHYSICS FOR NEET & AIIMS LIGHT The physical cause, with the help of which our eyes experience the sensation of vision, is known as light or the form of energy, which excites our retina an prouce the sensation of vision, is known as light. PROPERTIES OF VISIBLE LIGHT (i) (ii) (iii) No material meium is require for the propagation of light energy i.e. it travels even in vacuum. Its velocity is constant in all inertial frames i.e. it is an absolute constant. It is inepenent of the relative velocity between source an the observer. Its velocity in vacuum is maximum whose value is m/s. (iv) It lies in the visible region of electromagnetic spectrum whose wavelength range is from 4000 Å to 8000 Å. (v) (vi) (vii) (viii) (ix) (x) (xi) Its energy is of the orer of ev. It propagates in straight line. It exhibits the phenomena of reflection, refraction, interference, iffraction, polarisation an ouble refraction. It can emit electrons from metal surface i.e. it can prouce photoelectric effect. It prouces thermal effect an exerts pressure when incient upon a surface. It proves that light has momentum an energy. Its velocity is ifferent in ifferent meia. In rarer meium it is more an in enser meium it is less. Light energy propagates via two processes. (a) The particles of the meium carry energy from one point of the meium to another. (b) The particles transmit energy to the neighbouring particles an in this way energy propagates in the form of a isturbance. DIFFERENT THEORIES OF LIGHT. Newton's corpuscular theory of light.. Hygen's wave theory of light. 3. Maxwell's electromagnetic theory of light. 4. Plank's Quantum theory of light. 5. De-Broglie's ual theory of light.. Newton's corpuscular theory of light (i) This theory was enuciate by Newton. Characteristics of the theory (a) Extremely minute, very light an elastic particles are being constantly emitte by all luminous boies (light sources) in all irections (b) These corpuscles travel with the spee of light.. (c) When these corpuscles strike the retina of our eye then they prouce the sensation of vision. () The velocity of these corpuscles in vacuum is m/s. (e) The ifferent colours of light are ue to ifferent size of these corpuscles. (f) The rest mass of these corpuscles is zero. 44 etoosinia.com Inia s No. Online Coaching Institute

4 WAVE OPTICS TYPES OF INTERFERENCE (i) Constructive Interference When both waves are in same phase. So phase ifference is an even multiple of = nn = 0,,... (a) When path ifference is an even multiple of n = n = n(where n = 0,,...) (b) When time ifference is an even multiple of T (c) T t = n In this conition the resultant amplitue an Intensity will be maximum. A max = (a + a )I max = I + I + I I = ( I I ) (ii) Destructive Interference When both the waves are in opposite phase. So phase ifference is an o multiple of. = ( n ) n =,... (a) When path ifference is an o multiple of, = ( n ), n =,... (b) When time ifference is an o multiple of T, t = (n ) T, ( n=,...) In this conition the resultant amplitue an intensity of wave will be minimum. A min = (a a ) I = ( I I ) min E T TS OO IN S KEY PO (i) Interference follows law of conservation of energy. (ii) Average Intensity I av = I max I min I I a a (iii) Intensity with of slit (amplitue) I w a (iv) I max I a a a max min I min I I I a a a (v) Fringe visibility V = I I max max I I min min I w a I w a 00% when I min = 0 then fringe visibility is maximum i.e. when both slits are of equal with the fringe visibility is the best an equal to 00%. Ex. If two waves represente by y = 4 sin t an y = 3 sin ( t ) interfere at a point. Fin out the amplitue of the 3 resulting wave. Sol. Resultant amplitue A = a a a a cos = (4 ) 3.(4 )(3 )cos A ~ 6 3 etoosinia.com Stuy with Best Etoos Faculties of Kota 5

5 PHYSICS FOR NEET & AIIMS. Huygen`s Wave Theory : Huygen`s in 678 assume that a boy emits light in the form of waves. (a) Each point source of light is a centre of isturbance from which waves sprea in all irections. The locus of all the particles of the meium vibrating in the same phase at a given instant is calle a wavefront. (b) Each point on a wave front is a source of new isturbance, calle seconary wavelets. These wavelets are spherical an travel with spee of light in that meium. (c) The forwar envelope of the seconary wavelets at any instant gives the new wavefront. () In homogeneous meium, the wavefront is always perpenicular to the irection of wave propagation.. Coherent Sources : Two sources will be coherent if an only if they prouce waves of same frequency (an hence wavelength) an have a constant initial phase ifference. 3. Incoherent Sources : The sources are sai to be incoherent if they have ifferent frequency an initial phase ifference is not constant w.r.t. time. 4. Interference : YDSE 5. Resultant intensity for coherent sources I = I + I + II cos0 6. Resultant intensity for incoherent sources I = I + I 7. Intensity with of slit amplitue I W a I I I max a a I W a Imin I I a a nd 8. Distance of n th bright fringe X n Path ifference = n where n = 0,,, 3,... Distance of m th ark fringe X m m D etoosinia.com 73 Inia s No. Online Coaching Institute

6 WAVE OPTICS Ex. Sol. Young's ouble slit experiment is carrie out using microwaves of wavelength = 3 cm. Distance in between plane of slits an the screen is D = 00 cm. an istance in between the slits is 5 cm. Fin (A) the number of maximas an (B) their positions on the screen (A) The maximum path ifference that can be prouce = istance between the sources or 5 cm. Thus, in this case we can have only three maximas, one central maxima an two on its either sie for a path ifference of or 3 cm. (B) For maximum intensity at P, S P S P = ( y / ) D ( y / ) D = SOLVED EXAMPLE As D D D D Ex.3 A beam of light consisting of two wavelengths 6500 Å an 500 Å is use to obtain interference fringes in a young's ouble slit experiment. The istance between the slits is mm an the istance between the plane of the slits an screen is 0 cm. Sol. (A) Fin the istance of the thir bright fringe on the screen from the central maxima for the wavelength 6500 Å. (B) What is the least istance from the central maxima where the bright fringes ue to both the wave-lengths coincie? (A) Distance of thir bright fringe from centre of screen Ex. Sol. substiuting = 5 cm, D = 00 cm an = 3cm we get y = 75 cm Thus, the three maximas will be at y = 0 an y = 75 cm State two conitions to obtain sustaine interference of light. In Young's ouble slit experiment, using light of wavelength 400 nm, interference fringes of with 'X' are obtaine. The wavelength of light is increase to 600 nm an the separation between the slits is halve. If one wants the observe fringe with on the screen to be the same in the two cases, fin the ratio of the istance between the screen an the plane of the slits in the two arrangements. Conitions for sustaine interference of light (i) Sources shoul be coherent. (ii) There shoul be point sources fringe with D Here, D D an Ex.4 Sol. etoosinia.com Stuy with Best Etoos Faculties of Kota x 3 nd = m =.7 mm (B) When bright fringes coincie to each other then n = n n n So x 500Å Å 5 for minimum value of n & n n = 4, n = 5 n 0 D = 3 0 = m = 0.56 cm Two slits separate by a istance of mm are illuminate with re light of wavelength m. The interference fringes are observe on a screen place m from the slits. The istance between the thir ark fringe an the fifth bright fringe is equal to (A) 0.65 mm (C) 3.5 mm (B).65 mm (D) mm Distance between thir ark fringe an the fifth bright fringe 7 D = mm

7 PHYSICS FOR NEET & AIIMS Exercise # SINGLE OBJECTIVE NEET LEVEL. By corpuscular theory of light, the phenomenon which can be explaine is (A) Refraction (C) Diffraction (B) Interference (D) Polarisation. Accoring to corpuscular theory of light, the ifferent colours of light are ue to (A) Different electromagnetic waves (B) Different force of attraction among the corpuscles (C) Different size of the corpuscles (D) None of the above 3. Huygen s conception of seconary waves (A) Allow us to fin the focal length of a thick lens (B) Is a geometrical metho to fin a wavefront (C) Is use to etermine the velocity of light (D) Is use to explain polarisation 4. The iea of the quantum nature of light has emerge in an attempt to explain (A) Interference (B) Diffraction (C) Raiation spectrum of a black boy (D) Polarisation 5. Two coherent sources of light can be obtaine by (A) Two ifferent lamps (B) Two ifferent lamps but of the same power (C) Two ifferent lamps of same power an having the same colour (D) None of the above 6. By Huygen s wave theory of light, we cannot explain the phenomenon of (A) Interference (C) Photoelectric effect (B) Diffraction (D) Polarisation 7. The phenomenon of interference is shown by (A) Longituinal mechanical waves only (B) Transverse mechanical waves only (C) Electromagnetic waves only (D) All the above types of waves 8. Two coherent monochromatic light beams of intensities I an 4I are superpose. The maximum an minimum possible intensities in the resulting beam are (A) 5I an I (C) 9I an I (B) 5I an 3I (D) 9I an 3I 9. Light appears to travel in straight lines since (A) It is not absorbe by the atmosphere (B) It is reflecte by the atmosphere (C) Its wavelength is very small (D) Its velocity is very large 0. The iea of seconary wavelets for the propagation of a wave was first given by (A) Newton (C) Maxwell (B) Huygen (D) Fresnel. Young s experiment establishes that (A) Light consists of waves (B) Light consists of particles (C) Light consists of neither particles nor waves (D) Light consists of both particles an waves. In the interference pattern, energy is (A) Create at the position of maxima (B) Destroye at the position of minima (C) Conserve but is reistribute (D) None of the above 3. Monochromatic green light of wavelength m illuminates a pair of slits mm apart. The separation of bright lines on the interference pattern forme on a screen m away is (A) 0.5 mm (C).0 mm (B) 0. mm (D) 0.0 mm 4. In Young s ouble slit experiment, if the slit withs are in the ratio : 9, then the ratio of the intensity at minima to that at maxima will be (A) (B) /9 (C) /4 (D) /3 etoosinia.com 79 Inia s No. Online Coaching Institute

8 Exercise # SINGLE OBJECTIVE AIIMS LEVEL WAVE OPTICS. Huygen's principle is applicable to (A) Only light waves (B) Only soun waves (C) Only mechanical waves (D) For all the above waves. Which of the following phenomenon can not be explaine by the Huygen's theory- (A) Refraction (C) Diffraction (D) Formation of spectrum (B) Reflection 3. Accoring to huygen's theory of seconary waves, following can be explaine- (A) Propagation of light in meium (B) Reflection of light (C) Refraction of light (D) All of the above 4. The main rawback of huygen's theory was- (A) Failure in explanation of rectilinear propagation of lignt (B) Failure of explain the spectrum of white light (C) Failure to explain the formation of newton's rings (D) A failure of experimental verification of ether meium 5. Huygen's theory of seconary waves can be use to fin- (A) Velocity of light (B) The wavelength of light (C) Wave front geometrically (D) Magnifying power of microscope 6. Two coherent sources of intensities I an I prouce an interference pattern. The maximum intensity in the interference pattern will be : (A) I + I (B) I I (C) (I + I ) (D) ( I I ) 7. The colour are characterize by which of following character of light (A) Frequency (C) Wavelength (B) Amplitue (D) Velocity 8. Light has a wave nature, because- (A) the light travel in a straight line (B) Light exhibts phenomenon of reflection an re fraction (C) Light exhibits phenomenon interference (D) Light exhibits phenomenon of photo electric ef fect 9. Two wave are represente by the equations y = a sin t an y = a cos t.the first wave : (A) leas the secon by (B) lags the secons by (C) leas the secon by (D) lags the secons by 0. The phase ifference corresponing to path ifference of x is : (A) x x (C) (B) x (D) x. The resultant amplitue of a vibrating particle by the superposition of the two waves y = asin t 3 an y = a sin t is : (A) a (B) a (C) a (D) 3 a. The energy in the phenomenon of interference : (A) is conserve, gets reistribute (B) is equal at every point (C) is estroye in regions of ark fringes (D) is create at the place of bright fringes 3. Phenomenon of interference is observe : (A) only for light waves (B) only for soun waves (C) for both soun an light waves (D) none of above 84 etoosinia.com Stuy with Best Etoos Faculties of Kota

9 PHYSICS FOR NEET & AIIMS Exercise # 3 PART - MATRIX MATCH COLUMN. A monochromatic parallel beam of light of wavelength is incient normally on the plane containing slits S an S. The slits are of unequal with such that intensity only ue to one slit on screen is four times that only ue to the other slit. The screen is place perpenicular to x-axis as shown. The istance between slits is an that between screen an slit is D. Match the statements in column- with results in column-. (S S << D an << S S ) Column-I (A) The istance between two points on screen (P) having equal intensities, such that intensity Column-II D 3 at those points is th of maximum intensity. 9 (B) The istance between two points on screen (Q) having equal intensities, such that intensity at those points is 3 th of maximum intensity. 9 (C) The istance between two points on screen (R) having equal intensities, such that intensity at those points is 5 th of maximum intensity. 9 (D) The istance between two points on screen (S) having equal intensities, such that intensity D D 3D at those points is 7 th of maximum intensity. 9. A ouble slit interference pattern is prouce on a screen, as shown in the figure, using monochromatic light of wavelength 500nm. Point P is the location of the central bright fringe, that is prouce when light waves arrive in phase without any path ifference. A choice of three strips A, B an C of transparent materials with ifferent thicknesses an refractive inices is available, as shown in the table. These are place over one or both of the slits, singularly or in conjunction, causing the interference pattern to be shifte across the screen from the original pattern. In the column I, how the strips have been place, is mentione whereas in the column II, orer of the fringe at point P on the screen that will be prouce ue to the placement of the strips(s), is shown. Correctly match both the column. etoosinia.com 95 Inia s No. Online Coaching Institute

10 WAVE OPTICS Exercise # 4 PART - PREVIOUS YEAR (NEET/AIPMT). Which of the following phenomena exhibits particle nature of light? [CBSE AIPMT 00] (A) Interference (C) Polarisation. Transmission of light in optical fibre is (B) Diffraction (D) Photoelectric effect (A) scattering [CBSE AIPMT 00] (B) iffraction (C) polarisation (D) multiple total internal reflections 3. A beam of light compose of re an green rays in incient obliquely at a point on the face of a rectangular glass slab. when coming out on the opposite parallel face, the re an green rays emerge from [CBSE AIPMT 00] (A) two points propagating in two ifferent nonparallel irections (B) two points propagating in two ifferent parallel irections (C) one point propagating in two ifferent irections (D) one point propagating in the same irection 4. A telescope has an objective lens of 0 cm iameter an is situate at a istance of one kilometre from two objects. The minimum istance between these two objects, which can be resolve by the telescope, when the mean wavelength of light is 5000 Å, is of the orer of [CBSE AIPMT 004] (A) 0.5 m (C) 5 mm (B) 5 m (D) 5 cm 5. The angular resolution of a 0 cm iameter telescope at a wavelength of 5000 Å is of the orer of (A) 0 6 ra (C) 0 4 ra [CBSE AIPMT 005] (B) 0 ra (D) 0 6 ra 6. Which of the following is not ue to total internal reflection? [CBSE AIPMT 0] (A) Difference between apparent an real epth of a pon (B) Mirage on hot summer ays (C) Brilliance of imon (D) Working of optical fibre 7. In Young s ouble slit experiment, the slits are mm apart an are illuminate by photons of two wavelengths = 000 Å an = 0000 Å. At what minimum istance from the common central bright fringe on the screen m from the slit will a bright fringe from one interference pattern coincie with a bright fringe from the other? [NEET 03] (A) 8 mm (C) 4 mm (B) 6 mm (D) 3 mm 8. If the focal length of objective lens is increase, then magnifying power of [CBSE AIPMT 04] (A) microscope will increase but that of telescope ecrease (B) microscope an telescope both will increase (C) microscope an telescope both will ecrease (D) microscope will ecrease but that of telescope will increase 9. In the Young s ouble-slit experiment, the intensity of light at a point on the screen (where the path ifference is ) is K, ( being the wavelength of light use). The intensity at a point where the path ifference is /4, will be (A) K (B) K/4 (C) K/ [CBSE AIPMT 04] (D) zero 0. A beam of light of = 600 nm from a istant source falls ona single slit nm wie an the resulting iffraction pattern is observe on a screen m away. The istance between first ark fringes on either sie of the central bright fringe is [CBSE AIPMT 04] (A). cm (C).4 cm (B). mm (D).4 mm. The Young s moulus of steel is twice that of brass. Two wires of same length an of same area of cross-section, one of steel an another of brass are suspene from the same roof. It we want the lower ens of the wires to be at the same level, then the weight ae to the steel an brass wires must be in the ratio of [CBSE AIPMT 05] (A) : (B) : (C) 4 : (D) : etoosinia.com Stuy with Best Etoos Faculties of Kota 99

11 PHYSICS FOR NEET & AIIMS MOCK TEST STRAIGHT OBJECTIVE TYPE. Two light waves are given by, E = sin (00 t - k x + 30º) an E = 3 cos (00 t - k x + 60º) The ratio of intensity of first wave to that of secon wave is : (A) 3 (B) 4 9 (C) 9 (D) 3. The wavefront of a light beam is given by the equation x + y + 3z = c, (where c is arbitrary constant) then the angle mae by the irection of light with the y-axis is : (A) cos 4 (B) cos 4 (C) sin 4 (D) sin 4 3. If the ratio of the intensity of two coherent sources is 4 then the visibility [( max - min )/( max + min )] of the fringes is (A) 4 (B) 4/5 (C) 3/5 (D) 9 4. As shown in arrangement waves with ientical wavelengths an amplitues an that are initially in phase travel through ifferent meia, Ray travels through air an Ray through a transparent meium for equal length L, in four ifferent situations. In each situation the two rays reach a common point on the screen. The number of wavelengths in length L is N for Ray an N for Ray. In the following table, values of N an N are given for all four situations, The orer of the situations accoring to the intensity of the light at the common point in escening orer is : (A) 3 = 4 > > (B) > 3 = 4 > (C) > > 3 > 4 (D) > 3 = 4 > 5. If the istance between the first maxima an fifth minima of a ouble slit pattern is 7mm an the slits are separate by 0.5 mm with the screen 50 cm from the slits, then wavelength of the light use is : (A) 600 nm (B) 55 nm (C) 467 nm (D) 40 nm 6. In a YDSE: D = m, = mm an = 5000 n m. The istance of 00th maxima from the central maxima is: (A) m (B) 3 m (C) m (D) oes not exist 3 etoosinia.com 05 Inia s No. Online Coaching Institute

12 th Class Moules Chapter Details Physics 5 Moules Chemistry 5 Moules Mathematics 5 Moules Moule- PHYSICS. Physical Worl & Measurements. Basic Maths & Vector 3. Kinematics Moule-. Law of Motion & Friction. Work, Energy & Power Moule-3. Motion of system of particles & Rigi Boy. Gravitation Moule-4. Mechanical Properties of Matter. Thermal Properties of Matter Moule-5. Oscillations. Waves Moule-(PC) CHEMISTRY. Some Basic Conceps of Chemistry. Atomic Structure 3. Chemical Equilibrium 4. Ionic Equilibrium Moule-(PC). Thermoynamics & Thermochemistry. Reox Reaction 3. States Of Matter (Gaseous & Liqui) Moule-3(IC). Perioic Table. Chemical Boning 3. Hyrogen & Its Compouns 4. S-Block Moule-4(OC). Nomenclature of Organic Compouns. Isomerism 3. General Organic Chemistry Moule-5(OC). Reaction Mechanism. Hyrocarbon 3. Aromatic Hyrocarbon 4. Environmental Chemistry & Analysis Of Organic Compouns Moule- BIOLOGY. Diversity in the Living Worl. Plant Kingom 3. Animal Kingom Moule-. Morphology in Flowering Plants. Anatomy of Flowering Plants 3. Structural Organization in Animals Moule-3. Cell: The Unit of Life. Biomolecules 3. Cell Cycle & Cell Division 4. Transport in Plants 5. Mineral Nutrition Moule-4. Photosynthesis in Higher Plants. Respiration in Plants 3. Plant Growth an Development 4. Digestion & Absorption 5. Breathing & Exchange of Gases Moule-5. Boy Fluis & Its Circulation. Excretory Proucts & Their Elimination 3. Locomotion & Its Movement 4. Neural Control & Coorination 5. Chemical Coorination an Integration To purchase the books, go through the link belowhttp://

13 th Class Moules Chapter Details Physics 5 Moules Chemistry 5 Moules Mathematics 5 Moules Moule- PHYSICS. Electrostatics. Capacitance Moule-. Current Electricity. Magnetic Effect of Current an Magnetism Moule-3. Electromagnetic Inuction. Alternating Current Moule-4. Geometrical Optics. Wave Optics Moule-5. Moern Physics. Nuclear Physics 3. Solis & Semiconuctor Devices 4. Electromagnetic Waves Moule-(PC) CHEMISTRY. Soli State. Chemical Kinetics 3. Solutions an Colligative Properties Moule-(PC). Electrochemistry. Surface Chemistry Moule-3(IC). P-Block Elements. Transition Elements ( & f block) 3. Co-orination Compoun 4. Metallurgy Moule-4(OC). HaloAlkanes & HaloArenes. Alcohol, Phenol & Ether 3. Alehye, Ketone & Carboxylic Aci Moule-5(OC). Nitrogen & Its Derivatives. Biomolecules & Polymers 3. Chemistry in Everyay Life Moule- BIOLOGY. Reprouction in Organisms. Sexual Reprouction in Flowering Plants 3. Human Reprouction 4. Reprouctive Health Moule-. Principles of Inheritance an Variation. Molecular Basis of Inheritance 3. Evolution Moule-3. Human Health an Disease. Strategies for Enhancement in Foo Prouction 3. Microbes in Human Welfare Moule-4. Biotechnology: Principles an Processes. Biotechnology an Its Applications 3. Organisms an Populations Moule-5. Ecosystem. Bioiversity an Conservation 3. Environmental Issues To purchase the books, go through the link belowhttp://