Figure 1
Illustration: Top: www.dreamstime.com; Bottom: Pendry et al. [7]

Figure 1: (Top) A hot desert surface causes a refractive index gradient in the air above, causing rays of light to be refracted continuously to form a reflection in the road and hence the appearance of water. (Bottom) Similarly, a graded refractive index cloak can guide light around a hidden object so that an observer sees only that which is behind the cloak.