Refraction and reflection of planar waves in a discrete excitable medium is numerically investigated by using the Greenberg-Hasting model.It is fonnd that the medium is anisotropic because the speed of the planar wave depends on the excitability of the medium and the direction of wave propagation.The reflection,diffraction,refraction,double refraction and delayed refraction are observed by using the correct choice of model parameters.When the incident angle is larger than the critical angle,the reflection,which is a back refraction,takes place.The reflection angle changes with the incident angle.The refraction in certain situations obeys Shell's law.Also,our results demonstrate that the incident,refracted and reflected waves can have different periods.The reflected and refracted waves can disappear.
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