A Quiz on Electromagnetic Diffraction [Testing Ourselves]

Diffraction of Electromagnetic Waves

The general method to obtain solutions of the Maxwellian equations from scalar representatives is developed and applied to the diffraction of electromagnetic waves. Kirchhoff’s integral is modified to provide explicit expressions for these representatives. The respective integrals are then evaluated using the method of stationary phase in two dimensions. Hitherto unknown formulae for the polari...

On a class of electromagnetic diffraction-free beams.

We present a general theory of electromagnetic diffraction-free beams composed of uncorrelated Bessel modes. Our approach is based on the direct application of the nonnegativity constraint to the cross-spectral density tensor describing the electromagnetic field distribution. The field correlation properties are most conveniently derived in the spatial frequency domain, where the angular spectr...

Vector diffraction theory for electromagnetic waves.

The scalar Huygens-Fresnel principle is reformulated to take into account the vector nature of light and its associated directed electric and magnetic fields. Based on Maxwell's equations, a vector Huygens secondary source is developed in terms of the fundamental radiating units of electromagnetism: the electric and magnetic dipoles. The formulation is in terms of the vector potential from whic...

Ourselves

An ulcer on the foot: a quiz.

A 51-year-old man was admitted with an ulcer on the plantar surface of the left foot. The ulcer had appeared 3 weeks earlier, during a trip to the Solomon Islands, in the south-west Pacific Ocean, after he was stung by a shellfish while snorkelling near a reef. Twenty minutes after being stung, the patient experienced pruritus and a burning sensation at the site of sting. Five hours later, an a...