Emotional stimuli is the answer to your question.
Explanation:
Basaltic lava
Basaltic lava generally takes two distinct forms known by the Hawaiian terms pahoehoe and aa. Pahoehoe has a smooth wavy surface that resembles twisted rope. It advances by extruding molten toes of lava beneath a thin, flexible crust. As it travels pahoehoe lava often changes to blocky flows called aa.
A. it bends when light reaches an end of a barrier it will bend.
The electromagnetic that has a shorter wavelength is ultraviolet (UV)