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The nanometre is often used to express dimensions on an atomic scale: the diameter of a helium atom, for example, is about 0.06 nm, and that of a ribosome is about 20 nm. The nanometre is also commonly used to specify the wavelength of electromagnetic radiation near the visible part of the spectrum: visible light ranges from around 400 to 700 ...
Spectroscopy can detect a much wider region of the EM spectrum than the visible wavelength range of 400 nm to 700 nm in a vacuum. A common laboratory spectroscope can detect wavelengths from 2 nm to 2500 nm. [1] Detailed information about the physical properties of objects, gases, or even stars can be obtained from this type of device.
The wavelength of a sine wave, λ, can be measured between any two points with the same phase, such as between crests (on top), or troughs (on bottom), or corresponding zero crossings as shown. In physics and mathematics, wavelength or spatial period of a wave or periodic function is the distance over which the wave's shape repeats.
Natural sources produce EM radiation across the spectrum. EM radiation with a wavelength between approximately 400 nm and 700 nm is directly detected by the human eye and perceived as visible light. Other wavelengths, especially nearby infrared (longer than 700 nm) and ultraviolet (shorter than 400 nm) are also sometimes referred to as light.
The wavelength of visible light ranges from 390 to 700 nm. [4] The absorption spectrum of a chemical element or chemical compound is the spectrum of frequencies or wavelengths of incident radiation that are absorbed by the compound due to electron transitions from a lower to a higher energy state.
UVB light (< 315 nm) is filtered mostly by the cornea, and UVA light (315–400 nm) is filtered mostly by the lens. [20] The lens also yellows with age, attenuating transmission most strongly at the blue part of the spectrum. [20] This can cause xanthopsia as well as a slight truncation of the short-wave (blue) limit of the visible spectrum.
The bottom graph (Visible spectrum) is wavelength in units of nanometres (nm). Main article: Electromagnetic spectrum Generally, electromagnetic radiation (EMR) is classified by wavelength into radio waves , microwaves , infrared , the visible spectrum that we perceive as light, ultraviolet , X-rays and gamma rays .
300 nm – greatest particle size that can fit through a HEPA (high efficiency particulate air) filter (N100 removes up to 99.97% at 300 nm, N95 removes up to 95% at 300 nm) [84] 300–400 nm – near ultraviolet wavelength; 400–420 nm – wavelength of violet light (see Color and Visible spectrum) 420–440 nm – wavelength of indigo light