1.- Why our eyes can not see in other wavelengths?

Postgrado en Ingeniería Eléctrica.
Optomechanics.
Homework 3.
Name: Mariana Toscano Navarro.
Prof: Dr. Alejandro Farah Simón.
1.- Why our eyes can not see in other wavelengths?
R: For the vision to take place, the next requirements are necessary: an image should be
formed in the retina to stimulate its receptors (Rods and Cones), these generates nervous
impulses and they should be driven to the brain cortex.
The Rods (photosensitive cells of retina) have a protein called rhodopsin, which is very
sensitive to the light, when the light arrives to rods, starts a chemical change that releases
a nervous impulse from the rods.
The Cones are responsible for color vision. They require brighter light to function than rods
require and also have photosensitive substances:
 The first, more sensitive to short-wavelength (blue) called ‘cianolabo’, and its
maxim absorption is in 440 nm.
 The Second, more sensitive to medium-wavelength (green), called ‘clorolabo’, and
its maxim absorption is in 540 nm.
 The third, more sensitive to long-wavelength (red), called ‘eritrolabo’, and its
maxim absorption is in 590 nm.
Hence the chemical composition of the rhodopsin in the rods and others substances in the
cones involved, it is what determines the wavelengths at which the vision takes place [1].
2.-What is the spectral resolution of the vision of a black widow spider and a
bat?
Spiders.
The Spiders have simple eyes, compared to the compound eyes of many insects. Some
spiders have eight eyes, the number of eyes does not necessarily classify complexity or
define a more advanced vision system. Some provide forward vision while others may scan
to provide for peripheral vision. The eye signals going to the brain are combined to provide
peripheral vision, distance estimating, and image formation. Spiders do not have complex
lens focusing, but they have multiple eyes for limited color vision at different distances.
Their visual pigments transmit in the ultraviolet and green-spectral regions. Spider image
processing is astounding. Their brain processes several optical fields of different angular
dimensions at the same time. It is really amazing that their small brains carry out complex
image processing approaching that of complex man-made multi-sensor weapon or robotic
systems.
The black widow spider could be a true stealth weapon, if it could be controlled by man
[1].Catherine Parker Anthony Anatomia y Fisiologia (1986) Cap : 8pps:253.
at some reasonable cost. It has multiple eyes for fixed wide-field vision to see enemies,
find food, and to do close work in building webs.
Bats.
Although the eyes of most microbat species are small and poorly developed, leading to
poor visual acuity, none of them are blind. Vision is used to navigate microbats especially
for long distances when beyond the range of echolocation. It has even been discovered that
some species are able to detect ultraviolet light.
In addition to eyesight, bats use acoustic echo sensing, which is similar to what we
know as radar. Though they rely on visual clues for sight both day and night, when they
operate in darkness they place higher priority on their echo location capability. Their
unique image processing system is fast and efficient, which enables them to fly complex
paths through small passageways at low light levels.
[1].Catherine Parker Anthony Anatomia y Fisiologia (1986) Cap : 8pps:253.