Hw 8 due today hw 9 given out in chapter 34, we considered the propagation of light along a straight path ray. To understand the conditions for constructive and destructive interference in thin films. The interference produces a pattern of beautiful colors in white light, or dark and light bands in monochromatic light. No one has ever been able to define the difference between interference and diffraction satisfactorily. Lecture 5, p 2 today circular diffraction angular resolution rayleighs criterion minimum spot size interferometers michelson applications. Interference youngs interference experiment thin films coherence and incoherence michelson interferometer wave like characteristics of light huygens fresnel principle physical optics. Consider the two closely spaced spectral yellow lines of sodium na. To study the spreading of waves due to diffraction. Thus, diffraction plays a role in nearly all optical phenomena. The grating size can be expressed in terms of the number of grooves, n, and their spacing d. Typed notes for lecture 22 pdf handwritten notes for lecture 22 pdf 2mb textbook reading. Diffraction phenomena is calculated from interference of the waves originating from different points of a continuous source. Adam lark interference and diffraction 331 phase difference and coherence 332 interference in thin films 333 twoslit interference pattern 334 diffraction pattern of a single slit 335 using phasors to add harmonic waves 336 fraunhofer and fresnel. Physics 208 laboratory interference and diffraction.
Wide slit interference patterns with variable width slits. Interference superposition of waves in same direction graphical and mathematical phase and pathlength difference application to thin. Introduction to diffraction in materials science and. Diffraction produces a bright spot where poisson believed there would be darkness. This chapter is a direct continuation of the previous one, although the name has been changed from interference to diffraction. Diffraction from more than one electron add waves from different electrons total amplitude depends on interference effects gives information on relative positions for continuous electron density, replace sum by integral. If diffraction occurs for any finite aperture, we must revisit our ideas about multipleslit interference. For one, this is the main technique to split the light into spectral components according to the wavelengths used in modern spectrographs. Reflection and refraction n 1 n 2 law of reflection. S1 s2 d l bright constructive interference screen s1 s2 d l dark destructive interference. The virtual interference and diffraction apparatus is a very simple device with just a few controls.
Constructive interference occurs when the intensity at p reaches a maximum. Summary from last time the wave theory of light is strengthened by the interference and diffraction of light. Introduction to interference and diffraction in hindi. Interference as a wave phenomenon iinterference of light waves caused by superposition of waves intensity can increase or decrease. Lecture 35 diffraction and aperture antennas in this lecture you will learn. Reflection and interference from thin films inormalincidence light strikes surface covered by a thin film some rays reflect from film surface some rays reflect from substrate surface distance d further ipath length difference 2d causes interference from full constructive to full destructive, depending on. Though it contains basic discussion of the theory and physics of diffraction, this book. Optical instruments typically use only a limited portion of a wave. Suppose a monochromatic coherent source of light passes through three parallel slits, each separated by a. Interference and diffraction harvard natural sciences. Diffraction limited grating resolving power the angular width of a diffraction peak is limited by the physical size, w, of the grating seen tilted in projection at the diffracted angle.
A common example is the soap bubble we discussed in lecture, where reflections from the top and bottom surface of the soap film act as two light sources, which interfere at your eye. Interference of coherent waves in the doubleslit experiment waves at slits have to be coherent for interference to occur. Interference phenomena is calculates interference of the beams origination from discrete number of sources. Law of refraction revised c l f since c is constant wavelength, l n, and velocity of light, v n, are changing in medium but frequence, f, stays unchanged. Say a wave arrives at an opaque screen with a little hole in it. Interference at thin films constructive interference of r 1 phase shift 0. Pdf chapter 14 interference and diffraction setiyani n. Phys102 lecture 33 diffraction of light key points diffraction by a single slit diffraction in the doubleslit experiment limits of resolution diffraction grating and spectroscopy polarization references sfu ed. Doubleslit interference interferometers this lecture is part of 8. Interference and diffraction physics and astronomy. Constructive interference waves combine to give larger wave. Two different light bulbs in front of each slit will not give interference pattern. If you want, you can consider this plane wave to be generated plane wave wall figure 1 by a point source that is located a very large distance to the left of the wall. Interference patterns produced by a diffraction grating are projected on a screen.
This allowed for a reasonable explanation of reflection and refraction, but failed to account for diffraction and interference, which we discuss below. The intensity as a function of phase angle for a large number of oscillators of. Sometimes it is emphasized that we speak about diffraction picture when we consider interference from many sources as for example continous distribution of sources between the barriers in the figure above. Editor, the feynman lectures on physics new millennium edition.
Diffraction from a three dimensional periodic structure such as atoms in a crystal is called bragg diffraction. Gain and radiation pattern of aperture antennas ece 303 fall 2005 farhan rana cornell university diffraction and aperture antennas aperture antenna usually refers to a metallic sheet with a hole or an aperture of. Py212 lecture 25 interference and diffraction fun link. It shows how a beam of xrays is scattered into a characteristic pattern by a crystal. Xray wavelength is comparable with interatomic distances 1.
Diffraction of electromagnetic radiation gain and radiation pattern of aperture antennas ece 303 fall 2005 farhan rana cornell university diffraction and aperture antennas. How is the diffraction envelope and the position of the maxima of various orders affected by changes in the slit width and separation. Diffraction of waves in everyday life and applications. The data can be used to determine the crystals atomic structure. Real samples up to this point we have been considering diffraction arising from infinitely large crystals that are strain free and behave like ideally imperfect materials xrays only scattered once within a crystal crystal size and strain affect the diffraction pattern we can learn about them from the diffraction pattern. Diffraction can be observed for any kind of waves when diffraction occurs from several periodically arranged objects, the waves add up interference to produce maxima and minima of intensity to achieve this effect, the distance between the objects should be comparable to the wavelength in crystals, interatomic distances. Assuming diffraction limited optics, what is the minimum angular. Physical optics lecture notes pdf 44p this note covers the following topics. In the case of em wave, it is a pattern where changing electric field causes. Recalling resolution depends on only the total number of grooves and. Pes 2 fall 2014, spendier lecture 22page 1 lecture today. Lecture 53 interference and diffraction of em waves during our previous lectures we have been talking about electromagnetic em waves. Interference pattern formed by the diffracted light is called, for short diffraction pattern. Suppose a monochromatic coherent source of light passes through three parallel.
Interference pattern of the light diffracted on multiple slits in technology, of immense significance are interference patterns that are formed after diffraction on multiple parallel slits. Calculation of the diffraction pattern for light diffracted by two slits 2. Well use these same ideas when we study the interference of light waves in this chapter. Lecture demonstration services, science center, rm b08a, 1 oxford street, cambridge, ma 028. To understand how light diffracts through single slits and circular apertures. Interference of two one dimensional electromagnetic waves 3. Electricity and magnetism, as taught in spring 2002 by dr. Interference, diffraction 18 andpolarizationoflight in this chapter we treat light as waves to study interference, diffraction, and polarization. Each dot in this diffraction pattern forms from the constructive interference of xrays passing through a crystal. In constructive inter ference, the amplitude of the resultant wave at a given position or time is greater than that of either individual wave, whereas. If light from a sodium lamp fully illuminates a diffraction grating with 4000 slitscm, what is the angular.
Lecture notes optics pdf 57p this note covers the following topics. The transmissiontype diffraction grating flints on a stand just in front of a hene laser, and is brightly projected on the lecture room screen. Lecture 53 interference and diffraction of em waves. Our two most visually dramatic illustrations of thin film interference use either a soap film suspended in air from a 19 cm diameter circular frame, or a very thin layer of oil floating on top of water. Physical optics lecture notes pdf 44p download book. Constructive interference for all paths when d d path length difference 2d sin 1 2 3 path length difference 14 3d sin. Diffraction and the fourier transform diffraction examples diffraction by an edge arago spot the farfield. Diffraction of waves in everyday life and applications 2. One objection was that the interference experiment was inconsistent with the law of energy conservation at points of constructive interference, the light intensity is. If we have a set of n slits with finite apertures of width a, spaced a distance b apart, we expect the resultant intensity distribution to be a superposition of the amplitudes from n slits each one modified by the diffraction pattern due. You learned that waves interfere constructively at a point if their pathlength difference is an integer number of wavelengths. Properties of diffraction pattern for light diffracted by two slits 3. To understand how diffraction limits the resolution of optical instruments. The function in the first plot is simply the intensity we would see from a single slit.
The xray diffraction pattern of a pure substance is. Chapter 35 interference 1 diffraction of light 2 huygens principle 3 youngs interference experiment. Fundamentals and practical applications of diffraction for researchers, engineers, and students materials science relies heavily on diffraction for the analysis of materials. Now we have finished our analysis of the phenomena of dipole radiators qualitatively, and we must learn how to. So, we shall not worry about whether it is interference or diffraction, but continue. Interference and diffraction outline particles or waves youngs doubleslit experiment. Contrast with particle model of light ieffects and applications double slit single slit diffraction gratings antireflective coatings on lenses highly reflective coatings for mirrors. Lecture 15 february 23, 2016 1 outline 2 diffraction. The best we can do, roughly speaking, is to say that when there are only a few sources, say two, interfering, then the result is usually called interference, but if there is a large number of them, it seems that the word diffraction is more often used. Examples of thinfilm interference soap bubble thin oil film. This study is known as wave optics or physical optics. Missing orders in diffraction pattern produced by two slits.
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