Diffraction and Interference
Festa Buçinca
1647205
Phys 222
EXPERIMENT 4
diffraction and interference
Purpose: The aim of doing this experiment was to examine diffraction and interference effects of light passing through various apertures, and use the diffraction patterns obtained by single and double slit apertures to find the wavelength of the light source used.
Theory: We know that light can be described by two theories, namely the particle theory and the wave theory of light, each having its own experimental proofs. In this experiment, we examine the interference and diffraction phenomena of light, both of which can be described by the wave theory of light. While interference is just the superposition of waves, diffraction is also any deviation from geometrical optics that results from the obstruction of a wavefront of light. In other words, diffraction is considering the double-slit experiment by taking into account the width of the slit openings, too. Another way of distinguishing between interference and diffraction is to consider the interfering beams in diffraction phenomena as originating from a continuous distribution of sources, whereas the interfering beams in interference phenomena as originating from a discrete number of sources. This way of treatment of interference and diffraction is a result of Huygens’ principle which states that every point of a given wavefront of light can be considered a source of secondary spherical wavelets. Hence, superposition occurs between these secondary waves emitted from different parts of the wavefront, taking into account both their amplitudes and phases.
Diffraction effects can also be classified according to the mathematical approximations used in calculations. In the case of the light source and the observation screen being very far from the slit, relative to the slit width, the incident and diffracted waves are assumed to be plane and the diffraction type is called Fraunhofer, or far-field diffraction. In this case, as the
1647205
Phys 222
EXPERIMENT 4
diffraction and interference
Purpose: The aim of doing this experiment was to examine diffraction and interference effects of light passing through various apertures, and use the diffraction patterns obtained by single and double slit apertures to find the wavelength of the light source used.
Theory: We know that light can be described by two theories, namely the particle theory and the wave theory of light, each having its own experimental proofs. In this experiment, we examine the interference and diffraction phenomena of light, both of which can be described by the wave theory of light. While interference is just the superposition of waves, diffraction is also any deviation from geometrical optics that results from the obstruction of a wavefront of light. In other words, diffraction is considering the double-slit experiment by taking into account the width of the slit openings, too. Another way of distinguishing between interference and diffraction is to consider the interfering beams in diffraction phenomena as originating from a continuous distribution of sources, whereas the interfering beams in interference phenomena as originating from a discrete number of sources. This way of treatment of interference and diffraction is a result of Huygens’ principle which states that every point of a given wavefront of light can be considered a source of secondary spherical wavelets. Hence, superposition occurs between these secondary waves emitted from different parts of the wavefront, taking into account both their amplitudes and phases.
Diffraction effects can also be classified according to the mathematical approximations used in calculations. In the case of the light source and the observation screen being very far from the slit, relative to the slit width, the incident and diffracted waves are assumed to be plane and the diffraction type is called Fraunhofer, or far-field diffraction. In this case, as the
References: http://online.physics.uiuc.edu/courses/phys214/spring09/Lectures/Lect04.pdf http://bigbro.biophys.cornell.edu/~toombes/Science_Education/Laser_Diffraction/Diffraction_Lesson.pdf http://answers.yahoo.com/question/index?qid=20080509124425AAyW8bl http://physics.about.com/od/mathematicsofwaves/a/interference.htm URL: http://link.aps.org/doi/10.1103/PhysRevLett.68.472 DOI: 10.1103/PhysRevLett.68.472