DIFFRACTIONBryn McKay

Diffraction and Interference

Interference occurs when one or more wave are superimposed

Diffraction occurs whenever a wave encounters an object

Diffraction

 Large Aperture Small Aperture

Parallel light rays diverge and interfere with one another when passing through a aperture

Factors to this diffraction include: The size of the aperture The wavelength of light

Rays traveling at different distances interfere with one another

Sometimes they completely cancel each other

Diffraction is the slight bending of light as it passes around the edge of an object

A larger aperture with a smaller wave length the bending is unnoticeable.

When the two are closer in size the bend is noticeable to the naked eye

Examples

In the atmosphere Light bends around atmospheric particles Diffracted light can produce fringes of

light, dark or colored bands Light waves are similar to the water When sunlight comes in contact with

cloud droplets Light waves are altered and interact with one

another

Diffraction in Real Life

Diffraction Grating

Diffraction Grating

Diffraction grating is a structure with a repeating pattern

Grating Requirments

Efficiency Blaze Wavelength Wavelength Range Stray Light Resolving Power

HOLOGRAPHY

Holography

Simple Hologram

Made by superimposing two waves from the same light source

Two beams The reference beam hits the photographic plate

normally The object beam hits the plate at an angle

The relative phase between the two beams varies across the photographic plate

The two beams interfere with one another to form an interference pattern

The relative phase of object and reference beam is encoded as the maxima and minima of the fringe pattern

The fringe pattern acts as a diffraction grating

It is partly diffracted The object beam has been reconstructed The diffraction grating created by the two

waves interfering has reconstructed the object beam

This is a hologram

Vocab

Diffraction-the bending of waves around obstacles in their path

Aperture- an opening, as a hole, slit, crack, etc. Resolving Power- the ability of an optical

instrument to form separate images of two objects that are close together

Superimposing-to place, or set over, above, or on something else-to put or join as an addition

Fringe Pattern-one of the alternate light and dark bands produced by diffraction or interference

Reconstructed- Recreate or make again