Physical Geometric Optics Light propagates in the form of oscillations in an electromagnetic field, which expand from a point light source as evenly spaced and concentric wavefronts. The energy carried in the oscillations is measured in quantum packets known as photons. Light that appears green to the human eye has a wavelength of about 550 nanometers 0.00055 millimeters or 0.55 micrometers (hence submicron ). Visible wavelengths of moderately bright light range from about 750 nm orange red to 380 nm blue violet or 0.00075 to 0.00038 millimeters. Since AC is a common denominator, the sines differ in the ratio BC / B'A. The diagram shows that this is the ratio of the speed of light in the two media, which is measured as the index of refraction, and therefore the sine ratio is equal to the inverse refraction ratio n 2/ n 1. Thick Lens Optical Analysis Multiple Lens Optical Analysis Eyepiece Prescription Data. Optical Materials Optical Coatings This page describes the optical principles necessary to understand the design and function of telescopes and astronomical eyepieces. C /. Thus the frequency of "green" light at 550 nm is c / (wavelength in meters) or 545 trillion cycles per second. Light wavelengths are commonly measured in angstroms (10-10 meter nanometers (10-9 meter) or micrometers (10-6 meter).
This was demonstrated by the English naturalist Thomas Young as proof of the wave nature of light (diagram, left). In this situation light composed of parallel wavefronts from a single light source encounters a thin opaque barrier divided by two parallel, closely spaced and very narrow slits.