Laser Diffraction - Halo

Purpose

To demonstrate diffraction of laser light around small spheres.

Equipment

Laser with 8X collimator and glass plate with layer of lycopodium powder on laser cart.

Setup Time

5 min.

Description

Breathe on a glass plate and sprinkle the plate lightly with lycopodium powder to create diffraction sources for the laser light. Laser light shining around the tiny spheres of lycopodium powder is diffracted, creating a series of rings around the main spot on a distant screen. The average diameter of lycopodium powder spheres is about 4 microns. ◙◙Actually, this is a GLORY, not a HALO; a halo is a refraction/dispersion phenomenon while a glory is a diffraction phenomenon.

References

David Dutton, M Parker Givens, and Robert E. Hopkins, Some Demonstration Experiments in Optics Using a Gas Laser,◙Spectra-physics Laser Technical Bulletin, (1963). ◙Paul A. Young, A Student Experiment in Fresnel Diffraction, AJP 32, 367-369, (1964). ◙David Dutton, M. Parker Givens and Robert E. Hopkins, Some Demonstration Experiments in Optics Using a Gas Laser, AJP 32,◙355-361, (1964). ◙Haven Whiteside, Laser Optics Experiments and Demonstrations, AJP 33, 487-492, (1965). ◙Roy H. Biser, Modern Methods for the Study of Optical Diffraction, TPT 7, 158-161, (1969). ◙James Mahoney, Laser Interfer