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Ray optics

What is ray optics Ray optics is based on the assumption that light travels along straight lines. Taking average wavelength of visible light λ = 6000Å=6×10 7  m and diameter of pupil of human eye, a = 1mm=10-3m, the minimum distance a beam of light travels before its deviation from straight line path becomes significant is: Z F =a 2 / λ=(10 -3 ) 2 /6×10 -7 =1.67m. Z F  is called Fresnel distance. In day to day work, the  distance  involved is smaller than the Frensel distance. Therefore, we ignore deviation from straight line path i.e. we assume that light travels along straight lines. This is ray optics. ray optics Source of light There are three types of source of light Thermal sources, Gas discharge sources and luminescent sources. Photometry Photometry is a branch of Ray optics, which deals with the measurement of light energy. In this connection, the following four terms are to be clearly understood. 1) Luminous flux (φ) of a source of...