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I teach 16-19 year youth in technology and physics.
I have had serious problems this week explaining to them the physics behind "the fishermans problem": How to catch a fish with a spear in shallow waters.
I tried your java applet 1 and 2 - mostly no 2 with the user playing with the eye placement.
I try to imagine the fisherman pointing at the fish with a spear.
A suggestion could be to equip the fisherman with a spear pointing to the water. The spear could be represented by a straight line from one of the eyes - "the pointing eye" -the fisherman closes his other eye and points at the image of the fish.
My students got very frustrated when they discovered that a laser light beam is bent according to the law of refraction while the image of a spear will bend the opposite way.
I am now looking for an explanation for them !?
Thanks for the time you have spent at your homepage!
When we are stand in front of a mirror, we saw our image inside(behind) the mirror.
Because lights emitted from our body were reflected back at the mirror surface and enter out eye.
Our mind can trace those light paths which enter our eye and interpret that image was form inside(behind) the mirror.
However, we all know that it is the image (not the real object) which is inside (behind) the mirror.
The same effect occurs for the fishman problem:
From the above simulation,
red lines are the light paths for light emitted from the object, due to refraction, those two lines are bent at the water surface, and enter eye to have visual effect.
Our mind trace back with the
orange lines to find the location of the image.
And fishman will interpret the image as the real object.
I would suggest you find a transparent water tank, put some object inside.
Ask a student to point a long stick from eye position to the image of the object.
Also use a laser pointer pointing from eye along the stick to the water surface,
the llight from the laser pointer will hit the real object (light will be bent due to refraction at the water surface).