Energy & Green Tech

Bio-inspired solar devices boost stability, efficiency

Borrowing from cell membranes, the protective barriers around cells in all living organisms, Penn State scientists have developed a new, cost-effective method for creating bio-inspired solar devices that could improve the ...

Engineering

Bio-inspired device captures images by mimicking human eye

Drawing inspiration from nature, Penn State scientists have developed a new device that produces images by mimicking the red, green and blue photoreceptors and the neural network found in human eyes.

Engineering

World's first mass production of metalenses for visible wavelengths

Do you hate the camera bumps on the back of your smartphone? A new optical component called metalens—which was named one of the top 10 future technologies by the World Economic Forum in 2019—may be the answer. Composed ...

Engineering

AI-designed unidirectional imagers

Traditional optical imaging and communication systems, typically composed of lenses, perform imaging operations in both forward and backward directions. Similar to a pipe that enables liquid to flow through from one end to ...

Engineering

Shedding light on mechanisms of electrochemical energy storage

Understanding why certain materials work better than others when it comes to energy storage is a crucial step for developing the batteries that will power electronic devices, electric vehicles and renewable energy grids. ...

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Visible spectrum

The visible spectrum is the portion of the electromagnetic spectrum that is visible to (can be detected by) the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or simply light. A typical human eye will respond to wavelengths from about 380 to 750 nm. In terms of frequency, this corresponds to a band in the vicinity of 790–400 terahertz. A light-adapted eye generally has its maximum sensitivity at around 555 nm (540 THz), in the green region of the optical spectrum (see: luminosity function). The spectrum does not, however, contain all the colors that the human eyes and brain can distinguish. Unsaturated colors such as pink, and purple colors such as magenta are absent, for example, because they can only be made by a mix of multiple wavelengths.

Visible wavelengths also pass through the "optical window," the region of the electromagnetic spectrum that passes largely unattenuated through the Earth's atmosphere. (Blue light scatters more than red light, which is why the sky appears blue.) The human eye's response is defined by subjective testing (see CIE), but atmospheric windows are defined by physical measurement.

The "visible window" is so called because it overlaps the human visible response spectrum. The near infrared (NIR) windows lie just out of human response window, and the Medium Wavelength IR (MWIR) and Long Wavelength or Far Infrared (LWIR or FIR) are far beyond the human response region.

Many species can see wavelengths that fall outside the "visible spectrum". Bees and many other insects can see light in the ultraviolet, which helps them find nectar in flowers. Plant species that depend on insect pollination may owe reproductive success to their appearance in ultraviolet light, rather than how colorful they appear to us. Birds too can see into the ultraviolet (300-400 nm), and some have sex-dependent markings on their plumage, which are only visible in the ultraviolet range.

This text uses material from Wikipedia, licensed under CC BY-SA