Elements of Optics

This introduction is a brief treatment of the concepts and tools of optics encountered in the following chapters. Standard textbooks on optics can be consulted for more information. The wave theory of light is sufficient to explain all the characteristics of moiré. In what follows, we will describe a model of light consistent with the wave theory. A parallel beam of light propagating in the z direction is depicted at a given instant as a train of regularly spaced disturbances that vary with z as 2.1$$A = a\cos 2\pi \frac{z}{\lambda }$$For mathematical convenience, this expression is often replaced by the real part of the complex equation 2.1a$$A = a{{e}^{{i2\pi \frac{z}{\lambda }}}}$$ The symbol A describes the strength of the disturbance, which is usually viewed as the strength of an electromagnetic field at a point in space, particularly, the electric field strength; A will be called field strength. The coefficient a is a constant called the amplitude of the field strength. The field strength varies harmonically along z, where the distance between neighboring maxima is λ, called the wavelength.