Physics 106 Lesson 27 Interference and Diffraction The

  • Slides: 12
Download presentation
Physics 106 Lesson #27 Interference and Diffraction: The Wave Nature of Light Dr. Andrew

Physics 106 Lesson #27 Interference and Diffraction: The Wave Nature of Light Dr. Andrew Tomasch p 2405 Randall Lab p p atomasch@umich. edu

What Do We Know About Light? EM wave p Mostly travels in straight lines

What Do We Know About Light? EM wave p Mostly travels in straight lines (Ray Tracing) p In vacuum light travels at p Reflects with i = r p Refracts when passing between media with different index of refraction: p Bends toward the normal when passing into higher n → Snell’s Law

How do We Know Light is a Wave? p Distinguishing features of waves: •

How do We Know Light is a Wave? p Distinguishing features of waves: • Interference: two waves can add together and cancel • Diffraction: waves can travel around corners

Interference: Thin Films p Light waves traveling from one medium to another undergo partial

Interference: Thin Films p Light waves traveling from one medium to another undergo partial reflection and partial transmission at the interface of the two mediums

Soap Films

Soap Films

p Diffraction: n n The bending of waves around small obstacles and the spreading

p Diffraction: n n The bending of waves around small obstacles and the spreading of waves beyond small openings Small is defined in comparison to the wavelength The fact that we can hear sounds around corners and behind barriers involves both the diffraction and the reflection of sound waves

Huygens’ Principle Every point on a wave front acts as a source of tiny

Huygens’ Principle Every point on a wave front acts as a source of tiny wavelets that move forward with the same speed as the wave p The wave front at a latter instant is the surface that is tangent to the wavelets p

Diffraction Waves passing through narrow single opening bend and spread out. The diffraction of

Diffraction Waves passing through narrow single opening bend and spread out. The diffraction of light is only noticeable when the size of the opening is small compared to the wavelength of the light p The amount of bending increases as the size of the opening decreases p

Diffraction of a Water Wave The extent of the diffraction increases as the size

Diffraction of a Water Wave The extent of the diffraction increases as the size of the opening decreases.

Single-Slit Diffraction p This top view shows five sources of Huygens’ wavelets Demonstration

Single-Slit Diffraction p This top view shows five sources of Huygens’ wavelets Demonstration

The Diffraction Grating • We can replace the sine of the diffraction angle by

The Diffraction Grating • We can replace the sine of the diffraction angle by the ratio of two sides of a triangle The slits of the grating are perpendicular to the plane of the page.

X-ray Diffraction Complex diffraction patterns reveal the internal arrangements of crystals p Lower right

X-ray Diffraction Complex diffraction patterns reveal the internal arrangements of crystals p Lower right panel shows the DNA diffraction pattern that lead to the discovery of the double-helix structure p

Diffraction and Interference Double Slit Diffraction Diffraction isDiffraction and Interference Double Slit Diffraction Diffraction is
Applications of Diffraction Outline Interference Diffraction Examples DiffractionApplications of Diffraction Outline Interference Diffraction Examples Diffraction
Interference Diffraction Polarization interference diffraction polarization light asInterference Diffraction Polarization interference diffraction polarization light as
INTERFERENCE Constructive Interference Destructive Interference YOUNG TWOSLIT INTERFERENCEINTERFERENCE Constructive Interference Destructive Interference YOUNG TWOSLIT INTERFERENCE
XRay Diffraction and XRay Crystallography Diffraction l DiffractionXRay Diffraction and XRay Crystallography Diffraction l Diffraction
Chapter 19 Interference and Diffraction Diffraction is theChapter 19 Interference and Diffraction Diffraction is the
Interference and Diffraction Chapter 35 36 Diffraction WhatInterference and Diffraction Chapter 35 36 Diffraction What
Diffraction Light bends History of diffraction Diffraction solutionDiffraction Light bends History of diffraction Diffraction solution
diffraction methods diffraction methods Why are different diffractiondiffraction methods diffraction methods Why are different diffraction
Diffraction 27 7 The Diffraction Grating Diffraction gratingDiffraction 27 7 The Diffraction Grating Diffraction grating
Lecture 8 Diffraction Diffraction of Light Diffraction isLecture 8 Diffraction Diffraction of Light Diffraction is