It seems as if the street vibrates and has turned into a watery substance. I understand that it is due to the heat, but what exactly is happening? Is the image change in my eye, or actually on the road? And is this what is meant by a ‘Fata Morgana’ in the desert, ‘an oasis’? And why do you only see that from a distance and never close? Can it appear on all types of surfaces?
Answer
Hi Sarah,
This is indeed a mirage or mirage and is caused by the fact that the road is heated by the sun so that the air above the road also warms up in this way and is therefore somewhat warmer than the air not just above the road. Now the (optical) density of air also changes along with the temperature, so that light rays are ‘broken’ when they move from the colder air to the warm air. With the help of this lens effect, a light beam coming from the sky can be deflected and still end up in your eye. Your brain is naturally used to light going straight ahead so it will see the deflected light beam and think that this light is coming from somewhere on the road itself. While that skylight comes from the sky. In this way you see the sky as if it is in the road itself so that it can appear as if there is water there.
This effect can only take place at a far distance because the temperature differences are not large enough to make the light beam take a ‘sharp bend’ and you therefore need a great distance for the light to reach your eye.
Regards,
Lieven
Answered by
ir. Lieven Meert
Long-term economic growth and employment.
http://www.ugent.be
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