![]() Welders must wear protective eye shields because of the uv content of welding arcs can inflame the eyes. The eyes are quite susceptible to damage from ultraviolet radiation. The sun is a strong source of ultraviolet radiation, but atmospheric absorption eliminates most of the shorter wavelengths. The tissue effects of ultraviolet include sunburn, but can have some therapeutic effects as well. The shorter wavelengths reach the ionization energy for many molecules, so the far ultraviolet has some of the dangers attendent to other ionizing radiation. It is absorbed very strongly by most solid substances, and even absorbed appreciably by air. The region just below the visible in wavelength is called the near ultraviolet. An Angstrom unit = 0.1nm, so the visible light wavelengths would be 7500-4000 Angstroms. Some sources express the wavelengths in Angstrom units (1 Angstrom = 10 -10m). White light may be separated into its spectral colors by dispersion in a prism. In interactions with matter, visible light primarily acts to elevate electrons to higher energy levels. The narrow visible part of the electromagnetic spectrum corresponds to the wavelengths near the maximum of the Sun's radiation curve. HyperPhysics***** Electricity and Magnetism 003 - 4 x 10 14 HzĮlectromagnetic spectrum Greenhouse effect Infrared does not penetrate the atmosphere well, but astronomy in the infrared is carried out with the Spitzer Space Telescope. Infrared spectrometers are widely used to study the vibrational spectra of molecules. In interactions with matter, infrared primarily acts to set molecules into vibration. The range adjacent to the visible spectrum is called the "near infrared" and the longer wavelength part is called "far infrared". The wavelength range is from about 1 millimeter down to 750 nm. Raindrops can become natural prisms, causing rainbows when sunlight passes through.The term "infrared" refers to a broad range of frequencies, beginning at the top end of those frequencies used for communication and extending up the the low frequency (red) end of the visible spectrum. This is why a prism breaks white light up into a rainbow of different colors. When blue light passes from air through a dense glass prism, for example, it bends slightly more than red light does. Different colors of light bend by slightly different amounts. When light passes from one material to another material with a different density, is usually bends or changes course. Light travels most rapidly in a vacuum, and moves slightly slower in materials like water or glass. All forms of electromagnetic waves, including X-rays and radio waves and all other frequencies across the EM spectrum, also travel at the speed of light. At this speed, light could circle Earth more than seven times in one second! The lowercase letter "c" is often used to represent the speed of light in equations, such as Einstein's famous relation between energy and matter: E = mc 2. Light travels at a speed of 299,792 kilometers per second (about 186,282 miles per second). Ultraviolet radiation has shorter waves than blue or violet light, and thus oscillates more rapidly and carries more energy per photon than visible light does. Infrared radiation has longer waves than red light, and thus oscillates at a lower frequency and carries less energy. Visible light's neighbors on the EM spectrum are infrared radiation on the one side and ultraviolet radiation on the other. Red photons of light carry about 1.8 electron volts (eV) of energy, while each blue photon transmits about 3.1 eV. Red light has a frequency around 430 terahertz, while blue's frequency is closer to 750 terahertz. Shorter waves vibrate at higher frequencies and have higher energies. Blue and purple light have short waves, around 400 nm. Red light has relatively long waves, around 700 nm long. ![]() Our eyes perceive different wavelengths of light as the rainbow hues of colors. Light waves have wavelengths between about 400 and 700 nanometers (4,000 to 7,000 angstroms). Visible light is just one of many types of EM radiation, and occupies a very small range of the overall electromagnetic spectrum but because we can see light with our eyes, it has special significance to us. Light waves are the result of vibrations of electric and magnetic fields, and are thus a form of electromagnetic (EM) radiation. Visible light is one way energy moves around. Rainbows show how visible light is a combination of many colors.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |