## An Integral Result from Parseval’s Theorem

Introduction: In this Insight article,  Parseval’s theorem will be applied to a sinusoidal signal that lasts a finite period of time.  It will be shown that it necessarily follows that ## (\frac{\sin(2 x_o)}{x_o})( \frac{\pi}{2})=\int\limits_{-\infty}^{+\infty} \frac{\sin(x-x_o) \sin(x+x_o)}{(x-x_o)(x+x_o)} \, dx   ##. Note:  This integral result was computed by this author in 2009.  I have not done…

## The Diffraction Limited Spot Size with Perfect Focusing

Purpose:  The purpose of this Insights article is to give the reader a brief introduction to the principles behind diffraction limited focusing. The reader is assumed to be somewhat familiar with the concepts of diffraction theory and the Huygens sources that are used to compute a diffraction pattern. Perfect Focusing by paraboidal mirror:  When a…

## Frenet Equations in 2-D Which Result in the Cornu Spiral

This Insights article is intended as an introduction to the Frenet-Serret equations by showing an interesting application that results for a case in two-dimensional motion. The two-dimensional result for this case=the Cornu Spiral,  has some interesting associated mathematics that also arises in solutions of certain diffraction equations in optics. Frenet-Serret equations: The Frenet-Serret equations are…

## Permanent Magnets Explained by Magnetic Surface Currents

Introduction: The purpose of this Insight is to explain permanent magnets in a way that is in agreement with advanced textbooks on the subject, and that emphasizes the results in these textbooks without requiring nearly the mathematics that these textbooks use.    The magnetic fields from a permanent magnet can readily be understood by looking…

## Fabry-Perot and Michelson Interferometry: A Fundamental Approach

Fabry-Perot Effect: The Fabry-Perot effect is usually treated in most optics textbooks as the interference that results from multiple reflections of the two interfaces of a dielectric slab using a single incident beam. Michelson Interferometer: Meanwhile, the interference in the Michelson interferometer is usually described as the interference of a partially transmitted beam through the…