How do inferior mirages hide objects

After reading the thread about the little lake and its curvature illusions. I have to ask how does inferior mirages hide objects.
 

Mick West

Administrator
Staff member
Consider a classic "hot road" mirage.
Image result for hot road mirage

The road, including the yellow lines, are hidden.

How? They are hidden because the air above the road curves up the light rays, reflecting what is above it (sky, trees)
Image result for hot road mirage

You can't see the road, or things slightly above the road, because the light from them does not reach your eyes.

This is not an easy thing to visualize.
 

Mick West

Administrator
Staff member
For a more complex understanding, you need to think about the light paths to the camera (or eye, same thing). Here's a setup of six triangles at various distances. The top view is a side view showing the light paths. It's greatly magnified vertically so you can see what is going on.
No refraction is used here.
Metabunk 2020-03-04 10-29-29.jpg
The light blue line is the line of sight to the horizon. Notice that it just clips the last triangle #6, which you can just see peeking over the horizon. You can also see all of the first four triangles, and most of #5

Now let's add refraction by using the temperature curve shown, with the water a few degrees warmer than the air.
Metabunk 2020-03-04 10-34-18.jpg
Notice the downwards rays (blue) in the side view - a lot of them get bent upwards after the first two triangles.
This means you can't see the base of #3 and #4, very little of #5, and none of #6

You can play around with this in the simulator, here:
https://metabunk.org/refraction/?~(p~'Andy*2fWalter*20Inferior)_
 
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