Snell'S Law - Image Distortion
To illustrate a paradox involving Snell's law.
Plastic tank of water with ball bearing and washer pedestal.
The rays refracting in the horizontal and the vertical planes bend differently when exiting the dish, causing the ball bearing to become distorted when viewed through the top surface of the water. It apparently is a non-trivial problem to show that the image produced by a horizontal fan of rays is not at the same location as that produced by the more easily handled vertical fan of rays.
Jinsong Cui, A Demonstration of the Apparent Ellipticity of the Rising or Setting Sun, TPT 29, 566 (1991). John B. Johnston, Atmospheric Refraction, TPT 15, 308-309, (1977).