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  2. Encircled energy - Wikipedia

    en.wikipedia.org/wiki/Encircled_energy

    In optics, encircled energy is a measure of concentration of energy in an image, or projected laser at a given range. For example, if a single star is brought to its sharpest focus by a lens giving the smallest image possible with that given lens (called a point spread function or PSF), calculation of the encircled energy of the resulting image gives the distribution of energy in that PSF.

  3. Astronomical seeing - Wikipedia

    en.wikipedia.org/wiki/Astronomical_seeing

    The strength of seeing is often characterized by the angular diameter of the long-exposure image of a star (seeing disk) or by the Fried parameter r 0. The diameter of the seeing disk is the full width at half maximum of its optical intensity. An exposure time of several tens of milliseconds can be considered long in this context. The Fried ...

  4. Refractive error - Wikipedia

    en.wikipedia.org/wiki/Refractive_error

    In order to see a clear image, the eye must focus rays of light on to the light-sensing part of the eye – the retina, which is located in the back of the eye.This focusing – called refraction – is performed mainly by the cornea and the lens, which are located at the front of the eye, the anterior segment.

  5. Visual perception - Wikipedia

    en.wikipedia.org/wiki/Visual_perception

    The photoreceptor layer where transduction occurs is farthest from the lens. It contains photoreceptors with different sensitivities called rods and cones. The cones are responsible for color perception and are of three distinct types labelled red, green and blue. Rods are responsible for the perception of objects in low light. [42]

  6. Visible spectrum - Wikipedia

    en.wikipedia.org/wiki/Visible_spectrum

    The spectrum does not contain all the colors that the human visual system can distinguish. Unsaturated colors such as pink, or purple variations like magenta, for example, are absent because they can only be made from a mix of multiple wavelengths. Colors containing only one wavelength are also called pure colors or spectral colors. [8] [9]

  7. Energy level - Wikipedia

    en.wikipedia.org/wiki/Energy_level

    If it is at a higher energy level, it is said to be excited, or any electrons that have higher energy than the ground state are excited. Such a species can be excited to a higher energy level by absorbing a photon whose energy is equal to the energy difference between the levels. Conversely, an excited species can go to a lower energy level by ...

  8. Sarah Michelle Gellar Called Out of Work to See Taylor Swift ...

    www.aol.com/sarah-michelle-gellar-called-see...

    Sarah Michelle Gellar might consider herself a member of Taylor Swift's "Tortured Poets Department.". During a Friday, Dec. 20 appearance on The Drew Barrymore Show promoting Dexter: Original Sin ...

  9. Quantum optics - Wikipedia

    en.wikipedia.org/wiki/Quantum_optics

    Each particle carries one quantum of energy, equal to hf, where h is the Planck constant and f is the frequency of the light. That energy possessed by a single photon corresponds exactly to the transition between discrete energy levels in an atom (or other system) that emitted the photon; material absorption of a photon is the reverse process.