Mediaspace scheduled maintenance: Aug 25, 2026 07:00 - 12:00 AM. During this time, videos will be temporarily unavailable. Check status updates.

Lecture

Diffraction: Wave Phenomena and Interference

In course

PHYS-201(c): General physics : electromagnetism

Introduction à la mécanique des fluides, à l'électromagnétisme et aux phénomènes ondulatoires. ...

Description

This lecture covers diffraction phenomena when waves encounter obstacles, cracks, or holes, including sound waves and electromagnetic waves. It explains Fresnel and Fraunhofer diffraction, interference from a large number of sources, and the resolution limitations in imaging processes due to diffraction. The instructor demonstrates diffraction patterns by diffracting objects, such as spheres, slits, and circular apertures, and discusses the Rayleigh criterion for quantifying image resolution limitations.

This video is available exclusively on Mediaspace for a restricted audience. Please log in to MediaSpace to access it if you have the necessary permissions.

Watch on Mediaspace

Instructor

Giovanni Boero

Official source

Related concepts (32)

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.

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.

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.

Diffraction from slits

Diffraction processes affecting waves are amenable to quantitative description and analysis. Such treatments are applied to a wave passing through one or more slits whose width is specified as a proportion of the wavelength. Numerical approximations may be used, including the Fresnel and Fraunhofer approximations. Because diffraction is the result of addition of all waves (of given wavelength) along all unobstructed paths, the usual procedure is to consider the contribution of an infinitesimally small neighborhood around a certain path (this contribution is usually called a wavelet) and then integrate over all paths (= add all wavelets) from the source to the detector (or given point on a screen).

Kirchhoff's diffraction formula

Kirchhoff's diffraction formula (also called Fresnel–Kirchhoff diffraction formula) approximates light intensity and phase in optical diffraction: light fields in the boundary regions of shadows. The approximation can be used to model light propagation in a wide range of configurations, either analytically or using numerical modelling. It gives an expression for the wave disturbance when a monochromatic spherical wave is the incoming wave of a situation under consideration.

Related lectures (52)

Electromagnetic Waves and Optics

Covers the fundamentals of electromagnetic waves and optics, including interference phenomena, diffraction, refraction, and reflection of light.

Electromagnetic Waves: Reflection, Refraction, and Interference

Explores electromagnetic waves, wave optics, interference, and diffraction phenomena in experimental physics II.

Interference and Diffraction Phenomena

Explores how electromagnetic waves interfere and diffract, impacting their propagation and energy distribution over distance.

Electromagnetic Waves: Principles and Applications

Covers the principles of electromagnetic waves, including wave interference and diffraction.

Diffraction and Interference: Waves Phenomena