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Question
When you look at a spoon why is your reflection upside down?
Asked by: J. Been
Answer
Light rays travel in a straight line until they hit something. A light ray comes straight back only
when it hits an object dead on. If the surface of the object is slanted relative to the light, it
will cause the light to be reflected at an angle. So, a spoon's surface is curved, both from top to
bottom and side to side. And all the light that enters our eye does so in the same direction (we'll
call it the horizontal direction). Light from our toes hits the top of the spoon and, because of
it's 'downward' slant, gets redirected horizontally. And only light from our head gets reflected
horizontally from the bottom of the spoon. Since what we see is WHERE the light came from, we see
our toes above our head!
<------+\ Horizontal light hitting a slanted
<------++\ surface goes down... or upward moving light
<------+++\ goes left!
/
VVV
Light from Head
\
\ _
eye-toe --\---\\
eye X //
eye-head-/---//
/ //
/ //
/ // This
Light // is a
from LJ Spoon!
Toes
Answered by: Daniel Kurtz, B.S. EE, Cornell University
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