TAILIEUCHUNG - Smart.Materials.and.New.Technologies Episode 5

Tham khảo tài liệu ' episode 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Smart Materials and New Technologies The sun is the primary source of light for us and it also sets the standard of comparison for artificial light sources. While all objects produce radiation they do so in different parts of the spectrum. The sun emits radiation energy primarily 95 in a range of wavelengths from about 2x10 7 to 4x10 6m peaking in the visible part 45 of the solar radiation of the electromagnetic spectrum and extending into the ultraviolet 10 and near infrared 45 regions. The relative continuity of its intensity levels throughout the visible part of the spectrum provides an even level of illumination on surfaces allowing them to reflect any colors determined by their surface features. Conversely the early discharge lamps tended not only to be discontinuous across the spectrum but also had energy levels concentrated in narrow bandwidths. Even though we routinely talk about color as if it belongs to objects - blue water green grass red wagon - color belongs only to light. All surfaces are subtractive in that they can only subtract energy and color from light not add to it. For example the spectral distribution of a low-pressure sodium lamp has a very narrow bandwidth with wavelengths confined to the yellow range. When a blue car parks under this lamp the surface of the car can only reflect what is provided to it and in this case it can only reflect yellow. At best the car will appear to be a dark brown and it may even appear to be black if there are no yellow components in its paint. If the same car is still outside the next afternoon it will appear as the blue that was intended when the paint color was selected. We can describe the color of sources and the reflected color of objects with three quantities - energy wavelength and bandwidth. The energy level tells us how bright the wavelength tells us which hue and the bandwidth tells us with what saturation. Compare the following two spectral profiles. The first one is that of a laser. The energy level

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