infrared<\/strong>.<\/p>\nBy visible light we refer to the light that reaches us from the sun (sunlight) as well as the artificial light generated. We differentiate between the two spectra because they are different (the solar spectrum has other areas of the electromagnetic spectrum in addition to visible light).<\/p>\n
SOLAR LIGHT<\/strong><\/p>\nThe sun is a source of electromagnetic waves reaching the earth, most of which are in the visible light spectrum. The following figure shows the distribution of the waves arriving from the sun. Approximately 56% correspond to visible light, but waves with wavelengths shorter than ultraviolet and wavelengths longer than infrared are also received.<\/p>\n
<\/p>\n
What we know as light is the dispersion<\/strong> of electromagnetic waves of visible light made by air molecules.<\/p>\nPolarisation of light. Polarised light<\/p>\n
The flame from a candle, a Bunsen burner or one of those lighters used by all the
\nThe students are also surprised to see that the
\nflame does not cast any shadow on the wall (figures 18a and 18b). It can be explained as follows
\nis the photosphere, transparent to almost all radiation.<\/p>\n
INCANDESCENT LIGHT<\/strong><\/p>\nULTRAVIOLET LIGHT<\/strong><\/p>\nDepending on their wavelength, several subtypes of ultraviolet rays can be distinguished:<\/sup><\/p>\n\n\n\n
\n\nUltraviolet A (long wave)<\/td>\n | UVA<\/td>\n | 400 - 315<\/td>\n | 3,10 - 3,94<\/td>\n<\/tr>\n |
\nUltraviolet B (medium wave)<\/td>\n | UVB<\/td>\n | 315 - 280<\/td>\n | 3,94 - 4,43<\/td>\n<\/tr>\n |
\nUltraviolet C (shortwave)<\/td>\n | UVC<\/td>\n | 280 - 100<\/td>\n | 4,43 - 12,40<\/td>\n<\/tr>\n |
\nNear Ultraviolet\u00a0(near)<\/i><\/td>\n | NUV<\/td>\n | 400 - 300<\/td>\n | 3,10 - 4,13<\/td>\n<\/tr>\n |
\nMedium ultraviolet\u00a0(middle)<\/i><\/td>\n | MUV<\/td>\n | 300 - 200<\/td>\n | 4,13 - 6,20<\/td>\n<\/tr>\n |
\nFar ultraviolet\u00a0(far)<\/i><\/td>\n | FUV<\/td>\n | 200 - 122<\/td>\n | 6,20 - 10,16<\/td>\n<\/tr>\n |
\nLyman-alpha line<\/td>\n | H Lyman-\u03b1 \/ Ly-\u03b1<\/td>\n | 122 - 121<\/td>\n | 10,16 - 10,25<\/td>\n<\/tr>\n |
\nVacuum ultraviolet<\/td>\n | VUV<\/td>\n | 200 - 10<\/td>\n | 6,20 - 124<\/td>\n<\/tr>\n |
\nExtreme ultraviolet<\/td>\n | EUV<\/td>\n | 121 - 10<\/td>\n | 10,25 - 124<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n <\/p>\n Most of the ultraviolet radiation reaching the Earth from the Sun is in the forms UV-A, UV-B and UV-C; UV-C radiation does not reach the surface as it is absorbed by oxygen and ozone in the atmosphere; UV-B radiation is partially absorbed by ozone and only reaches the Earth's surface to a minimal extent, so that the radiation reaching the Earth's surface is mainly of the UV-A type.<\/p>\n The types of UV radiation (A, B and C) are related to the damage they cause to humans: UV-C radiation is the most damaging to life.<\/p>\n Moderate absorption of UV-B ultraviolet rays allows the synthesis of vitamin D in the skin, which is necessary for the absorption of calcium and its deposition in the bones.<\/sup><\/p>\n |