Mirage

An unusual morning and midday of extreme equatorial equinox sun made me set aside the Friday quiz and head outdoors to look for a mirage as a way to wrap up a week of refraction and reflection. Mirages are the refraction that looks like a reflection.

The road is not quite long enough and not quite dark enough to generate a larger mirage, but there is one just barely visible in the above image.

There is no water there. Just an illusion. A mirage.

The light from the sun bounces off the distance car. Some of the rays bounce down towards the road. The air directly above the road is heated by the asphalt to a higher temperature than the air further above the surface of the road. This leads to a lower density for the air in the few centimeter above the asphalt. The light bends, refracts upwards, back towards the higher density air further above the road, traveling upwards to our eye. The light never reflected off of the road, the light bent in an arc. The result is an image that our brain interprets as a reflection. Our brain also interprets the reflection as a phenomenon associated with water, so the brain tells us that the reflection must be water on the road.