 FIZIKA A 10 (2001) 4 , 141-154

### CORRELATION BETWEEN DIFFRACTION OF LIGHT BY CIRCULAR APERTURE AND CLOSE-RANGE INTERACTION ENERGY OF TWO CHARGED SPHERES

Department of Physics, University of Zagreb, Bijenička 32, HR-10000 Zagreb

Dedicated to Professor Kseno Ilakovac on the occasion of his 70th birthday

##### Received 22 June 2001; revised manuscript received 9 January 2002 Accepted 21 January 2002        Online 6 April 2002

It is shown that the coefficients Ak of angles qk, corresponding to the minima of light intensity in the diffraction by a circular aperture, can successfully be described by a function which appears in the electrostatic interaction energy between two uniform surface-charged spheres. The coefficient Ak defines the angle qk by sinqk = Akl/d, k = 1,2,3, Ľ , where l is the wavelength of light and d is the diameter of the aperture. These coefficients may be correlated with a dimensionless function fb/R, encountered in the relation of the interaction energy terms of two spheres of equal radii R, with uniformly-distributed surface charges q and q˘ and at a mutual distance b. The total interaction energy, i.e. the Coulomb potential energy, is W = qq˘/(4pe0b), where e0 is the permitivity of vacuum. This energy contains two terms, a positive one W(+) = W fb/R and negative one W(-) = W (1-fb/R). The correlation between Ak and the function fb/R is given by Ak - k = u + v fb/R,k, where u and v are constants. Coefficients Ak obtained by this correlation agree with those defined by the diffraction method within an error of 10-3% at k = 1, and gradually diminishing to 10-4% at k = 10.