Top Banner
Modelling synchrotron radiation using visible light Helen Lye ACER February 2007
37

Modelling synchrotron radiation using visible light Helen Lye ACER February 2007.

Dec 31, 2015

Download

Documents

Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Page 1: Modelling synchrotron radiation using visible light Helen Lye ACER February 2007.

Modelling synchrotron radiation using visible light

Helen Lye

ACER

February 2007

Page 2: Modelling synchrotron radiation using visible light Helen Lye ACER February 2007.

Workshop activities

Warning

• Keep direct laser light out of your eyes;

• Point the laser away from you and from other people;

• Look away from bright reflections;

• Set up laser equipment so that the beam is below eye level.

Page 3: Modelling synchrotron radiation using visible light Helen Lye ACER February 2007.
Page 4: Modelling synchrotron radiation using visible light Helen Lye ACER February 2007.

http://www.arpansa.gov.au/pubs/rhs/rhs36.pdf

http://www.vicphysics.org/teachers/photonics.html

Page 5: Modelling synchrotron radiation using visible light Helen Lye ACER February 2007.
Page 6: Modelling synchrotron radiation using visible light Helen Lye ACER February 2007.

Interference and diffraction

• Diffraction: spreading of a wave at right angles to the direction of travel when it passes through a gap or around a narrow object. For visible light, the spreading results in a diffraction pattern of light and dark spots or bands.

Page 7: Modelling synchrotron radiation using visible light Helen Lye ACER February 2007.

Interference and diffraction

• Interference: pattern of constructive and destructive interference formed when two or more waves intersect.

Page 8: Modelling synchrotron radiation using visible light Helen Lye ACER February 2007.

Examples• Sound wave interference results in louder

and softer sounds in particular positions relative to the sound source.

• Visible light interference results in light and dark regions in particular positions relative to the light source.

• X-ray interference results in high and low intensities of X-rays in particular positions relative to the source.

Page 9: Modelling synchrotron radiation using visible light Helen Lye ACER February 2007.
Page 10: Modelling synchrotron radiation using visible light Helen Lye ACER February 2007.
Page 11: Modelling synchrotron radiation using visible light Helen Lye ACER February 2007.

Single slit and two slits close together

Page 12: Modelling synchrotron radiation using visible light Helen Lye ACER February 2007.
Page 13: Modelling synchrotron radiation using visible light Helen Lye ACER February 2007.
Page 14: Modelling synchrotron radiation using visible light Helen Lye ACER February 2007.

Diffraction of laser light through a vertical opening of decreasing width. Note that as the opening gets narrower, the amount of diffraction in the horizontal direction increases.

Page 15: Modelling synchrotron radiation using visible light Helen Lye ACER February 2007.
Page 16: Modelling synchrotron radiation using visible light Helen Lye ACER February 2007.

Hexagonal hole

Page 17: Modelling synchrotron radiation using visible light Helen Lye ACER February 2007.

Student investigations

Diffraction effects

• Use laser light to observe the diffraction pattern formed by different fibres.

screenobject

laser

Page 18: Modelling synchrotron radiation using visible light Helen Lye ACER February 2007.

Student investigations

Diffraction effects

• Use laser light to observe the diffraction pattern formed by different fibres.

• Sketch each pattern

Page 19: Modelling synchrotron radiation using visible light Helen Lye ACER February 2007.

Diffraction effects

• take any measurements that you could use to calculate the diameter of each fibre.

LengthNumber of dark bands

Distance from object to screen

Page 20: Modelling synchrotron radiation using visible light Helen Lye ACER February 2007.

Diffraction in two dimensions

Two dimensional grids

screenobject

laser

Page 21: Modelling synchrotron radiation using visible light Helen Lye ACER February 2007.
Page 22: Modelling synchrotron radiation using visible light Helen Lye ACER February 2007.

Gauze ribbon (chiffon ribbon) diffraction pattern. STAVCON November 24 2006 Thomas

Cherry lab fourth floor.Red laser level about 2m away;

gauze taped to laser and hanging down.

Page 23: Modelling synchrotron radiation using visible light Helen Lye ACER February 2007.

Two dimensional helix model

• Pair of bolts or screws

• The laser beam must line up with the gap between the threads.

Blu-tack

Two bolts

screen

laser

Page 24: Modelling synchrotron radiation using visible light Helen Lye ACER February 2007.

Two dimensional helix model

• Pair of bolts or screws

• The laser beam must line up with the gap between the threads.

Page 25: Modelling synchrotron radiation using visible light Helen Lye ACER February 2007.

X-ray diffraction pattern of DNA

Page 26: Modelling synchrotron radiation using visible light Helen Lye ACER February 2007.

Quantitative

measurements

laser

screenGauze ribbon

Count dark bandsMeasure width of pattern

Measure distance

Page 27: Modelling synchrotron radiation using visible light Helen Lye ACER February 2007.

Diffraction gratings

Page 28: Modelling synchrotron radiation using visible light Helen Lye ACER February 2007.

When light of a single wavelength , like the 632.8nm red light from a helium-neon laser strikes a diffraction grating it is diffracted to each side in multiple orders. Orders 1 and 2 are shown to each side of the direct beam.

Page 29: Modelling synchrotron radiation using visible light Helen Lye ACER February 2007.

While directing the 632.8 nm red beam of a helium-neon laser through a 600 lines/mm diffraction grating, a cloud was formed using liquid nitrogen. You can see the direct beam plus the first and second orders of the diffraction. Another way to visualize the

diffraction is to take a time exposure while sweeping a ground glass through the beams. This "paints in" the beams of the diffracted laser light.

Page 30: Modelling synchrotron radiation using visible light Helen Lye ACER February 2007.

The illustration shows the hydrogen spectrum. The hydrogen gas in a thin glass tube is excited by an electrical discharge and the spectrum can be viewed through the grating.

Page 31: Modelling synchrotron radiation using visible light Helen Lye ACER February 2007.

The tracks of a compact disc act as a diffraction grating, producing a separation of the colors of white light. The nominal track separation on a CD is 1.6 micrometers, corresponding to about 625 tracks per millimeter. For red light of wavelength 600 nm, this would give a first order diffraction maximum at about 22° .

Page 32: Modelling synchrotron radiation using visible light Helen Lye ACER February 2007.
Page 33: Modelling synchrotron radiation using visible light Helen Lye ACER February 2007.

Data

• Measure the angle between the incident laser light and the normal of the CD.

• Measure the angle between the normal to the CD and the n=-1 order and the

• normal and n=1 order.

• Use the grating formula to determine the track spacing on the CD for each set of data

Page 34: Modelling synchrotron radiation using visible light Helen Lye ACER February 2007.

Diffraction pracs from http://www.ssabsa.sa.edu.au/suppo

rt/science/2phy/2phy-menu.htm

Page 35: Modelling synchrotron radiation using visible light Helen Lye ACER February 2007.

Safe laser inspection deviceExplore your toothpaste

Gorazd PlaninˇsiˇcFaculty for Mathematics and Physics, University of Ljubljana,

Sloveniaand

The House of Experiments, Ljubljana, Slovenia

SPECIAL FEATURE: HEALTH AND BEAUTYPHYSICS EDUCATION 41 (4)www.iop.org/journals/physed

Page 36: Modelling synchrotron radiation using visible light Helen Lye ACER February 2007.

Figure 1. What can we find out about the iridescentpieces on the toothpaste package?

Safe Laser Inspection Device made from onehemisphere of a painted Christmas ball.

Diffraction patterns produced by the shiny part of a toothpaste package using red and green laser lightrespectively.

Page 37: Modelling synchrotron radiation using visible light Helen Lye ACER February 2007.