  We present observations of the diffraction, refraction, and reflection of a
global extreme-ultraviolet (EUV) wave propagating in the solar corona. These
intriguing phenomena are observed when the wave interacts with two remote
active regions, and they together exhibit the wave property of this EUV wave.
When the wave approached AR11465, it became weaker and finally disappeared in
the active region, but a few minutes latter a new wavefront appeared behind the
active region, and it was not concentric with the incoming wave. In addition, a
reflected wave was also observed simultaneously on the wave incoming side. When
the wave approached AR11459, it transmitted through the active region directly
and without reflection. The formation of the new wavefront and the transmission
could be explained with diffraction and refraction effects, respectively. We
propose that the different behaviors observed during the interactions may
caused by different speed gradients at the boundaries of the two active
regions. For the origin of the EUV wave, we find that it formed ahead of a
group of expanding loops a few minutes after the start of the loops' expansion,
which represents the initiation of the associated coronal mass ejection (CME).
Based on these results, we conclude that the EUV wave should be a nonlinear
magnetosonic wave or shock driven by the associated CME, which propagated
faster than the ambient fast-mode speed and gradually slowed down to an
ordinary linear wave. Our observations support the hybrid model that includes
both fast wave and slow non-wave components.
