Editing Refraction (section)

==Mechanical waves==

===Water===
{{Main|Water wave refraction}}
[[File:Beach and waves (2784111859).jpg|thumb|Water waves are almost parallel to the beach when they hit it because they gradually refract towards land as the water gets shallower.]]
[[Water wave]]s travel slower in shallower water. This can be used to demonstrate refraction in [[ripple tank]]s and also explains why waves on a shoreline tend to strike the shore close to a perpendicular angle. As the waves travel from deep water into shallower water near the shore, they are refracted from their original direction of travel to an angle more normal to the shoreline.<ref>{{cite web |url=http://www.coastal.udel.edu/ngs/waves.html |title=Shoaling, Refraction, and Diffraction of Waves |access-date=2009-07-23 |publisher=University of Delaware Center for Applied Coastal Research |archive-url=https://web.archive.org/web/20090414215458/http://www.coastal.udel.edu/ngs/waves.html |archive-date=2009-04-14 |url-status=dead }}</ref>

===Sound===
{{Main|Refraction (sound)}}
In [[underwater acoustics]], refraction is the bending or curving of a sound ray that results when the ray passes through a [[sound speed gradient]] from a region of one sound speed to a region of a different speed. The amount of ray bending is dependent on the amount of difference between sound speeds, that is, the variation in temperature, salinity, and pressure of the water.<ref>{{cite book
 |title     = Navy Supplement to the DOD Dictionary of Military and Associated Terms
 |date      = August 2006
 |publisher = [[United States Navy|Department Of The Navy]]
 |url       = https://www.nwdc.navy.mil/Documents/NTRP_1-02.pdf
 |id        = NTRP 1-02
}}{{dead link|date=April 2025|bot=medic}}{{cbignore|bot=medic}}</ref>
Similar [[acoustics]] effects are also found in the [[Earth's atmosphere]]. The phenomenon of [[refraction of sound]] in the atmosphere has been known for centuries.<ref>[[Mary Somerville]] (1840), ''[[On the Connexion of the Physical Sciences]]'', J. Murray Publishers, (originally by Harvard University)</ref> Beginning in the early 1970s, widespread analysis of this effect came into vogue through the designing of urban [[highway]]s and [[noise barrier]]s to address the [[meteorological]] effects of bending of sound rays in the lower atmosphere.<ref>{{cite journal|doi=10.1007/BF00159677|title=Analysis of highway noise|year=1973|author=Hogan, C. Michael|journal=Water, Air, & Soil Pollution|volume=2|pages=387–392|issue=3|bibcode=1973WASP....2..387H|s2cid=109914430}}</ref>