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An EM spectrum from left to right displays atmosphere opaque and ionosphere opaque. The middle part displays optical window, infrared windows and radio window. The different bands close to visible spectrum are gamma rays, x rays, ultraviolet, infrared and radio spectrum. The gamma rays are related with cancer therapy, the x-rays are related with medical diagnosis, ultraviolet rays are related with sterilization, infrared is related with heating, night vision and radio spectrum is related with communication, radar, radio and TV broadcasting, and radio astronomy. The wavelength in meters from left to right is labeled, 10 to the negative 15 power to 10 to the 8th power. Frequency in hertz from left to right is labeled, 10 to the 23rd power to 1.