Trans. Antennas and Propagation, AP-28, (4) pp. 571-575. 14, (19)(614). Van Der Pol, B. and Bremmer, H. (1937) The diffraction of electro- CCIR (1970) CCIR interim method for estimating sky-wave field magnetic waves from an electrical point source round a finitely strength and transmission loss at frequencies between the ap- conducting sphere, with applications to radiotelegraphy and the proximate limits of 2 and 30MHz, CCIR Report 252-2, New theory of the rainbow (2 parts). Phil. Mag., XXIV, pp. 141-176, Delhi. and pp. 825-863. CCIR (1982a) Prediction of sky-wave field strength between 150kHz and 1600kHz, CCIR Recommendation 435-4, XVth Vogler, L.E. (1964) Calculation of groundwave attenuation in the Plenary Assembly, VI, Geneva. far diffraction region. Radio Sci. J. Res. MBS., 68D, (7) pp. 819-826. CCIR (1982b) Analysis of sky-wave propagation measurements for the frequency range 150 to 1600kHz, CCIR Recommendation Yagi, H. (1928) Beam Transmission of Ultra Short Waves, Proc. 431-3, XVth Plenary Assembly, VI, Geneva. IRE, 26, pp. 715-741. This page intentionally left blank Optics and vision D R Heath BSc PhD CPhys MInstP British Aerospace Contents Basic concepts of optical radiation 7/3 The optical spectrum 7/3 Radiometry and photometry 7/3 Units of measurement 7/4 Instrumentation 7/6 The human eye 7/9 Structure of the eye 7/9 The eye as an optical instrument 7/10 Defects of vision 7/11 Interaction of light with matter 7/11 References 7/13 This page intentionally left blank Basic concepts of optical radiation 7/3 Basic concepts of optical radiation The wavenumber (cm-1) is the reciprocal of the wavelength measured in centimetres, (cm) = wavenumber (cm-1 In describing the measurement of light and its interaction with matter, three complementary properties of electromagnetic radia- The term monochromatic light is often encountered and refers to tion need to be invoked: ray, wave and quantum. At microwave and the situation where most of the electromagnetic energy is concen- longer wavelengths it is generally true 