A mirage can occur when a continuous variation in the refractive index of the air causes light rays to follow a curved path. As a result, the image we see is displaced from the location of the object.1 If the image appears higher in the air than the object, it is called a “superior” mirage, while if it appears lower it is called an “inferior” mirage.2 The most common example of an inferior mirage is when, on a hot day, a stretch of dry road off in the distance appears to be wet (see Fig. 1). Many lab activities have been described that simulate the formation of superior mirages. In these demonstrations light beams curve downward as they pass through a nonuni‐form fluid.3–6 Much less common are laboratory demonstrations of upward‐curving light rays of the kind responsible for inferior mirages. This paper describes a simple version of such a demonstration.

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Our container is a rectangular Plexiglas tank 26 cm long, 6 cm high, and 1 cm wide.
8.
With our particular tank, 25 ml of each liquid is an appropriate amount.
9.
A bit of nondairy creamer also works well.
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