How Animals see more than humans? Fact File 38


The Night time world is never closed for nocturnal animals. Unlike humans, many animals possess adaptations that allow them to see even when the night sky is very dark. Animals have developed amazing adaptations to their environments. Most nocturnal animals have large eyes relative to their body size. This adaptation, along with the ability to dilate their pupil far wider than humans can, maximizes the amount of light entering into the eye.

Not all animals see the world as humans do. For many animals, the world is seen in fuzzy shades of gray, or very “washed out” and pale colors. But some animals can see in total darkness, or even see colors beyond the visual spectrum, that humans have never seen. Still others can use binocular vision to spot prey from thousands of feet away.

Nocturnal mammals have rods in the retina with unique properties that make enhanced night vision possible. The nuclear pattern of their rods changes shortly after birth to become inverted. Inverted rods have heterochromatin in the center of their nuclei and euchromatin and other transcription factors along the border. The outer nuclear layer in nocturnal mammals is thick due to the presence of millions of rods  to process the lower light intensities of a few photons. Light is passed to each nucleus individually.

Many animals have a tissue layer called the Tapetum lucidum at  the back of the eye that reflects light back through the retina. This increases the amount of light entering into the retina. This is found in many nocturnal animals and some deep sea animals. This causes the phenomenon of eye shine in these animals. Tapetum lucidum is absent in human eye.The shining of eyes in Dogs and Cats in vehicle head light is due to this reflective retina.Some animals have Guanine crystals in the eye that shines and reflect light.

1. Dog and Cats – They have night vision and can see moving objects rather than the stationary ones. Their eyes are much more sensitive to movement. Dogs and cats are color blind and see only very pale shades of color but they have better peripheral and night vision.

2. At night , some snakes use Pit Organs to sense infrared rays from the prey. Pit organs can pick up infrared heat signals from warm objects in their surroundings.

3. Bees can see light between wavelengths 300 nm & 650 nm and they can see polarized light.

4. Bats can detect warmth of an animal from about 16 cm away using its “nose-leaf“.
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PIR Sensor


Infrared is the invisible radiation lies between the Visible and Microwave portions of the electromagnetic spectrum. The term Infra means below the ability to detect visually and the term Red means colour of the light with low energy level. The Near infrared is close to the red portion of visible light and the Far infrared is close to the microwave region. Far infrared is thermal and we feel it as heat by the temperature sensors in our skin. Short and Near infrared rays cannot be detected since these are invisible as well as cool. Active infrared rays are produced from semiconductor sources but natural objects like animals including human beings emit infrared rays from the body heat. Humans at normal body temperature emits Infrared rays at the wavelength of 10 microns.PIR Sensors are used in surveillance systems to detect moving persons in protected areas.



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PIR Sensor


Infrared is the invisible radiation lies between the Visible and Microwave portions of the electromagnetic spectrum. The term Infra means below the ability to detect visually and the term Red means colour of the light with low energy level. The Near infrared is close to the red portion of visible light and the Far infrared is close to the microwave region. Far infrared is thermal and we feel it as heat by the temperature sensors in our skin. Short and Near infrared rays cannot be detected since these are invisible as well as cool. Active infrared rays are produced from semiconductor sources but natural objects like animals including human beings emit infrared rays from the body heat. Humans at normal body temperature emits Infrared rays at the wavelength of 10 microns.PIR Sensors are used in surveillance systems to detect moving persons in protected areas.



Continue reading “PIR Sensor”