Appendix 1 The mathematical background to holography

Any traveling wave that varies in a cosinusoidal manner when viewed as it passes a fixed point can be described by an equation of the form

a ¼ A cosð!tÞ In this equation a and t are variables: a is the instantaneous amplitude at a time t. A and ! (omega) are constants. A is the peak or maximum amplitude; and ! is called the angular frequency, which is related to the wavelength by the relationship

! ¼ 2

and is measured in radians.