Building a static light scattering instrument

(supervisor: Dave Langstaff)

Nature of project: experimental, software

Available to full-time physicists only.

Project description and methodology

The size of particles and droplets in aerosols, suspensions or emulsions can be measured by Static Light Scattering. The technique is based on the fact that rays are refracted both when they enter and when they leave a medium with different refractive index. If the two refracting interfaces are curved, a net deflection of the ray from its incident path is observed. Since the interface curvature increases with decreasing particle size, the size (and shape) of the particles can be deduced from the scattering pattern. Applications of the technique therefore range from measurements of atmospheric pollution and milk fat content to sedimentation dynamics and composition control in chemical reactors.

There is an instrument in the department which has been constructed to measure the MIE scattering from a sample vial. A previous project improved the design of this instrument. This project is to evaluate the effectiveness of the instrument in its current state and to calibrate the instrument based on the light scattering from a known suspension of latex spheres. Once the instrument is calibrated, it should be used to characterise a solution of milk in water.

A successful project will develop beyond the above in one/some of the following directions:
A software program (MIEPlot) to predict the light scattering from different suspensions is available from http://www.philiplaven.com/mieplot.htm

Results from this program should be compared with results taken from the laboratory instrument.

When considering where to take your project, please bear in mind the time available. It is preferable to do fewer things well than to try many and not get conclusive results on any of them. However, sometimes it is useful to have a couple of strands of investigation in parallel to work on in case delays occur.

This project is only available as a Y3 project.

Initial literature for students:

  1. E Hecht; Optics; San Francisco: Addison-Wesley (2002)
  2. I Weiner, M Rust, TD Donnelly; Am J Phys 69 (2001) 129
  3. D Lehner, G Kellner, H Schnablegger, O Glatter; J Colloid Interf Sci 201 (1998) 34
  4. HC van de Hulst, Light Scattering by Small Particles, New York: Dover 1981

Novelty, degree of difficulty and amount of assistance required

The outcome of the project is predictable, but the challenge lies in the process of drawing up a feasible design based on calculations of optical parameters as well as careful project planning.

Steve Fearn will help with the assembly of the instrument, and Rudi Winter will be available to discuss the optical specifications and design as well as give background on the light scattering technique.

Project milestones and deliverables (including timescale)

milestoneto be completed by
survey of optical and mechanical resolution enhancementsend of November
design plans for any components to be built or bought inChristmas
instrument assembledend of February
test patterns collected, manual writtenEaster

Students taking this project will have to submit a full risk assessment form