Anti-radiation missile Anti-radiation missile An anti-radiation missile (ARM) is a missile designed to detect and home in on an enemy radio emission source. Typically, these are designed for use against an enemy radar, although jammers and even radios used for communications can also be targeted in this manner. Most ARM designs to date have been intended for use against ground-based radars. Commonly carried by specialist aircraft in the Suppression of Enemy Air Defenses (SEAD) role (known to the United States Air Force as "Wild Weasels"), the primary purpose of this type of missile is to degrade enemy air defenses in the first
Refraction wave vector depend on the wave speed this requires a change in direction of the wave vector. The relevant wave speed in the discussion above is the phase velocity of the wave. This is typically close to the group velocity which can be seen as the truer speed of a wave, but when they differ it is important to use the phase velocity in all calculations relating to refraction. A wave traveling perpendicular to a boundary, i.e. having its wavefronts parallel to the boundary, will not change direction even if the speed of the wave changes. Refraction of light can