Question

Explain the following:

• How many lenses do human eyes have and what are they called? How do they work to show us objects both close and far away? (Remember that simple glass lenses only have one focal length, unlike our eyes.) What happens as we age?
• How do humans perceive color? Can our brains be fooled into thinking we see a color (let’s say yellow) when we are not actually looking at yellow light? (Hint: This relates to TV and computer screens.)

Discuss the eyes of other animals—let’s say cats, flies, and hummingbirds. What do these animals’ eyes do better than humans’? Why does the animal benefit from these different abilities? Does the animal lack visual abilities that humans have?

Answer 1

Human eye has two lenses. They are called as

1. Cornea

2. Crystalline lens.

In these two lenses crystalline lens has the ability to change its shape, which changes its focal length and hence allowing us to focus on both nearby as well as far away objects clearly.

As we age cells in eye weakens hence causing stiffness in eye lens which results in focusing nearby objects very hard. This condition in human eye is called Presbyopia.

Due to ageing its become hard to see in dim light, also reaction time of pupil increases to change amount of light.

Human eye perceive color due to light sensitive cell present on the retina of the eye - Rod and Cone cells. These cells receive light rays and produces nerve impulse which is transfered to brain through optic nerve.

Yes, our brains are fooled into thinking that we see a color instead we not. As cone cells on our retina usually detects red, blue and green colors. So to form YELLOW color on T.V. or Computer screen red and green color are activated simultaneously for short time which confuses brain to say Yellow color as wavelength of yellow lies in between Red and Green color.

Due to high concentration of rod cells and low concentration of cone cells on the retina, these animals are better in seeing objects in dim light (night time) which human eye can't. Also due to eye position these animal have wider area of vision.

Due to these abilities they can pray better in night time. Also due to larger range of vision they can save themselves from being attacked.

Yes, animal lack visual abilities as they cannot see colors as sharp as we can. Which makes there vision of world less colourful.