Editing Light (section)

==Optics==
{{Main|Optics}}
[[File:Linear visible spectrum.svg|center|upright=2]]

The study of light and the interaction of light and [[matter]] is termed ''[[optics]]''. Optics has different forms appropriate to different circumstances. [[Geometrical optics]], appropriate for understanding things like eyes, lenses, cameras, [[fiber optics]], and mirrors, works well when the wavelength of light is small in comparison to the objects it interacts with. [[Physical optics]] incorporates wave properties and is needed understand diffraction and interference. [[Quantum optics]] applies when studying individual photons interacting with matter.<ref>{{Cite book |last=Hecht |first=Eugene |title=Optics |date=1998 |publisher=Addison-Wesley |isbn=978-0-201-83887-9 |edition=3. |location=Reading, Mass. Harlow}}</ref>{{rp|33}} 

=== Surface scattering ===

A [[Transparency (optics)|transparent]] object allows light to [[Transmittance|transmit]] or pass through. Conversely, an [[Opacity (optics)|opaque]] object does not allow light to transmit through and instead [[Reflection (physics)|reflecting]] or [[Absorbance|absorbing]] the light it receives. Most objects do not reflect or transmit light [[Specular reflection|specularly]] and to some degree [[Scattering|scatters]] the incoming light, which is called [[Gloss (optics)|glossiness]]. Surface scattering is caused by the [[surface roughness]] of the reflecting surfaces, and internal scattering is caused by the difference of [[refractive index]] between the particles and [[Transmission medium|medium]] inside the object. Like transparent objects, [[translucent]] objects allow light to transmit through, but translucent objects also scatter certain wavelength of light via internal scattering.<ref>{{Cite book |last=Berns |first=Roy S. |url= |title=Billmeyer and Saltzman's Principles of Color Technology |publisher=[[Wiley (publisher)|Wiley]] |others=Fred W. Billmeyer, Max Saltzman |year=2019 |isbn=978-1-119-36668-3 |edition=4th |location=Hoboken, NJ |oclc=1080250734}}</ref>

===Refraction===
{{Main|Refraction}}
[[File:Optical refraction at water surface.jpg|thumb|Due to refraction, the straw dipped in water appears bent and the ruler scale compressed when viewed from a shallow angle.]]

Refraction is the bending of light rays when passing through a surface between one transparent material and another. It is described by [[Snell's Law]]:

:<math>n_1\sin\theta_1 = n_2\sin\theta_2\ .</math>

where θ<sub>1</sub> is the angle between the ray and the surface [[Normal (geometry)|normal]] in the first medium, θ<sub>2</sub> is the angle between the ray and the surface normal in the second medium and n<sub>1</sub> and n<sub>2</sub> are the [[Index of refraction|indices of refraction]], ''n'' = 1 in a [[vacuum]] and ''n'' > 1 in a [[Transparency and translucency|transparent]] [[Chemical substance|substance]].

When a beam of light crosses the boundary between a vacuum and another medium, or between two different media, the wavelength of the light changes, but the frequency remains constant. If the beam of light is not [[orthogonality|orthogonal]] (or rather normal) to the boundary, the change in wavelength results in a change in the direction of the beam. This change of direction is known as [[refraction]].

The refractive quality of [[lens (optics)|lenses]] is frequently used to manipulate light in order to change the apparent size of images. [[Magnifying glass]]es, [[Glasses|spectacles]], [[contact lens]]es, [[microscope]]s and [[refracting telescope]]s are all examples of this manipulation.