MOTION MOUNTAIN

the eye and the brain: biological image acquisition and processing 179
Challenge 180 ny
Challenge 181 s
F I G U R E 129 What is the angle between the thin lines between the squares?
F I G U R E 130 The Lingelbach lattice: do you see white, grey, or black dots at the crossings?
right needle will disappear, and vice versa. This shows that the image inside the eye, on
the retina, is inverted. Are you able to complete the proof?
An urban legend, spread by many medical doctors and midwives to this day, claims
that newborn babies see everything upside down. Can you explain why this idea is
wrong?
Two additional experiments can show that retinas acquire inverted images. If you
push very lightly on the inside of your eye (careful!), you will see a dark spot appear
on the outside of your vision field. And if you stand in a dark room and ask a friend to
look at a burning candle, explore his eye: you will see three reflections: two upright ones,
reflected from the cornea and from the lens, and a dim third one,upside-down, reflected
from the retina.
Motion Mountain – The Adventure of Physics copyright © Christoph Schiller June 1990–November 2015 free pdf file available at www.motionmountain.net