PARTICLE SIZE MEASUREMENT

Shine an expended He-Ne laser beam through a plate dusted with lycopodium powder to construct circular rings on the screen which are nearly spherical and have a very uniform average diameter. The quality of the ring depends on the evenness of dusting Wavelength of given laser source of light Where n - Order of diffraction l - Wavelength of laser used in meter D - Distance between glass plate and screen in meter xn - Distance between central bright spot and the nth fringe in meter