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Lecture

Diffraction by a Grating: Understanding Light Dispersion

In course

MICRO-561: Fundamentals of biomicroscopy

Introduction to the basic operational principles of the most commonly used optical microscopes such as widefield and fluorescence.
Introduction to essential microscopy components such as lenses, objectives, filters, cameras and light sources. ...

Description

This lecture covers the concept of diffraction by a grating, which consists of parallel linear grooves that diffract light in specific directions. The diffraction spots on a screen indicate unique diffraction angles, leading to constructive interference. The dispersion effect of a grating is explained, showing how different orders of diffraction are related to wavelength. Additionally, the lecture discusses the use of diffraction gratings to disperse white light and analyze samples using UV-Vis spectroscopy. The relationship between diffraction angle, period size, and spatial frequency is explored, emphasizing how smaller features diffract more light. Examples of diffraction phenomena in microscopy are provided, illustrating how particle size influences light scattering and angle of spreading.

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Instructors (2)

Hatice Altug

2020-current Full Professor at the Institute of Bioengineering, EPFL, Switzerland2013-2020 Associate Professor (with tenure) at the Institute of Bioengineering, EPFL, Switzerland 2013 Associate Professor (with tenure) at Electrical and Computer Engineering Department of Boston University, USA 2007-2013 Assistant Professor (tenure-track) at Electrical and Computer Engineering Department of Boston University, USA 2007 Post-doctoral Fellow at Center for Engineering in Medicine of Harvard Medical School, USA 2000-2007 PhD. in Applied Physics at Stanford University, USA 1996-2000 B.S. in Physics at Bilkent University, Turkey

Arne Seitz

04/1996-06/2000 Scientific co-worker at Philipps-University of Marburg, Dep. of Physical Chemistry 07/2000-10/2002 Post Doc at Max-Planck Unit for Structural Molecular Biology in Hamburg 11/2002-11/2005 Post Doc at European Molecular Biolohy Laboratory (EMBL), Cell Biology and Cell Biophysics Programme 11/2005-03/2009 Staff Scientist at Advanced Light Microscopy Facility, EMBL 04/2009- Head of Bioimaging and Optics platforme (BIOP), Ecole Polytechnique Fédérale de Lausanne (EPFL)

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Related concepts (28)

Diffraction

Diffraction is the interference or bending of waves around the corners of an obstacle or through an aperture into the region of geometrical shadow of the obstacle/aperture. The diffracting object or aperture effectively becomes a secondary source of the propagating wave. Italian scientist Francesco Maria Grimaldi coined the word diffraction and was the first to record accurate observations of the phenomenon in 1660.

Fraunhofer diffraction

In optics, the Fraunhofer diffraction equation is used to model the diffraction of waves when plane waves are incident on a diffracting object, and the diffraction pattern is viewed at a sufficiently long distance (a distance satisfying Fraunhofer condition) from the object (in the far-field region), and also when it is viewed at the focal plane of an imaging lens. In contrast, the diffraction pattern created near the diffracting object and (in the near field region) is given by the Fresnel diffraction equation.

Infrared spectroscopy

Infrared spectroscopy (IR spectroscopy or vibrational spectroscopy) is the measurement of the interaction of infrared radiation with matter by absorption, emission, or reflection. It is used to study and identify chemical substances or functional groups in solid, liquid, or gaseous forms. It can be used to characterize new materials or identify and verify known and unknown samples. The method or technique of infrared spectroscopy is conducted with an instrument called an infrared spectrometer (or spectrophotometer) which produces an infrared spectrum.

Spectroscopy

Spectroscopy is the field of study that measures and interprets the electromagnetic spectra that result from the interaction between electromagnetic radiation and matter as a function of the wavelength or frequency of the radiation. Matter waves and acoustic waves can also be considered forms of radiative energy, and recently gravitational waves have been associated with a spectral signature in the context of the Laser Interferometer Gravitational-Wave Observatory (LIGO).

Fresnel diffraction

In optics, the Fresnel diffraction equation for near-field diffraction is an approximation of the Kirchhoff–Fresnel diffraction that can be applied to the propagation of waves in the near field. It is used to calculate the diffraction pattern created by waves passing through an aperture or around an object, when viewed from relatively close to the object. In contrast the diffraction pattern in the far field region is given by the Fraunhofer diffraction equation. The near field can be specified by the Fresnel number, F, of the optical arrangement.

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