“The human eye is an organ of vision. A vital organ of vision it plays a very important role not only in life but also the human body. The human eye is the organ which gives us the sense of sight, allowing us to learn more about the surrounding world than we do with any of the other four senses. The eye allows us to see and interpret the shapes, colors, and dimensions of objects in the world by processing the light they reflect or emit. The eye is able to see in bright light or in dim light, but it cannot see objects when there is no light.
Video Courtesy – Youtube, 7activestudio
We use our eyes in almost every activity we perform, whether reading, watching television, and in other countless ways. Now days, good vision is critical and essential to conducting activities of daily living easily. It is important for language, and affects developmental learning, communicating, working, health and quality of life. It is very important to take care of your eyesight. Imagine not being able to read the newspaper, see if you are going to be hit by a car, or drive a car. Without a healthy vision you will be forced to rely on other to cross the street or go for grocery shopping, becoming many times very inconvenient. Most people probably would agree that sight is the sense they’d value more than the rest”.
Referred from http://www.odec.ca/projects/2006/thog6n2/importance.html
In my case our eyes wearing a very beautiful smile as because it has a punctual behavior. Every day when we open our eyes in the morning we can satisfy that still we are breathing, because eyes gives us a purpose to alive in this entire Planet. If animals are come without eyes in the Earth then there will be every nights for everyday. So, it has a huge role in our life. And when we close our eyes it feels like something statue as like as our life stop in one place. We cannot imagine our life without eyes. All we know that without eye we can’t do anything. So, save your eyes and make your life colorful.
How to use properly Computers, Mobile phones and Tablets for saving your Eyes from
Now a days, every one using Tablets, Smart phones, Laptop etc. But some of them are not know that how to use it properly. And misuse of that should become very dangerous. So, in my instructions you can use it safely. Following instructions are:-
1. When you are using your computers don’t go to watch it front to front. For that computer workstations often are arranged for adult uses by making slightly bend chairs, this can change the viewing angle from your position. Kindly try to use your computers viewing the screen slightly downwards at a 15 degree angle. Among other suggestions feet should be rest comfortably on the floor.
2. Don’t use your Smartphone and tablet in dark room because, it can affect your eyes directly and it may cause Eye strain.
“3. Blink, Blink and blink again your eyes when you are using Smartphone because, blinking often (and for more than a second) keeps your eyes moist and reduces dryness and irritation. We tend blink about a third less than we normally would when we stare lovingly at our precious Smartphone screens, which starves our poor peepers of protective tears. Keep your eyes wet by blinking about 10 times every 20 minutes or so and you should be good to go. Blinking often helps refocus your eyes, too.
4. Take a break from looking at your screen every 20 minutes for 20 seconds while looking at something 20 feet away doing so relaxes your eye muscles.
Video Courtesy – Youtube, CNET
5. Adjust your brightness. Having your screen too bright or too dark stresses your eyes out and can cause problems maintaining focus. To eliminate either issue in about a matter of seconds, simply go into your Smartphone settings and adjust your screen brightness so it’s about the same as the light level in the Environment around you. Wait – that is unless you’re in the pitch black dark squinting at your Smartphone in bed, which, by the way, can lead to insomnia and less sex.
6. Tweak your text size and contrast.
Adjusting your smart phones text contrast and size also provides a little much-needed relief. It makes it easier to read web content
Email messages, smudges and fingerprints.
7. Hold your Smartphone farther away. It’s ok. You don’t have to put it all the way down. I promise most people tend to hold their cell phones only about 8 inches from their faces. Not good. Try holding yours at least 16 to 18 inches away from your eyes to give your eyes a break. It might feel funny at first but shouldn’t take long to get used to”. Referred from https://www.entrepreneur.com/article/232665
How image is formed behind the Retina?
“Because light rays diverge in the all directions from their source, the set of rays from each point in space that reach the pupil must be focused. The formation of focused image on the photo-receptors of the retina depends on the refraction (bending) of light by the cornea and the lens. The cornea is responsible for most of the necessary refraction, a contribution easily appreciated by considering the hazy out-of focus images experienced when swimming underwater. Water, unlike air, has a refractive index close to that of the cornea; as a result, immersion in water virtually eliminates the refraction that normally occurs at the air/cornea interface. The lens has considerably less refractive supplied by the lens is adjustable allowing, allowing objects at various distances from the observer to be brought into sharp focus on the retinal surface”.
Referred from http://www.ncbi.nlm.nih.gov/books/NBK11079/?_e_pi_=7%2CPAGE_ID1O%2C6942180832
In that case how do photo-receptors work?
Photo-receptors contain chemicals, when they are hit by light than it should be change. This causes an electrical signal, which is then goes to the brain with the optic nerve. Different types of photo-receptors allow us to see an huge range of light from starlight to full sunshine, and all the colors of the rainbow.
Referred from http://www.sciencemuseum.org.uk/whoami/findoutmore/yourbrain/whatareyoursenses/howdoyousee/howdoyoureyeswork
Description on lens?
A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction. “It forms an image by refraction of light at its two bounding surfaces. In general, a lens is made of glass and is bounded by two regular curved surfaces; or by one spherical surface and a plane spherical surface is very easy to make. Therefore, most lenses are made of spherical surface and have a wide range of curvatures. Other transparent materials such as quartz, fused silica and plastics are also used in making lenses. A single lens with two refracting surfaces is a simple lens. We study here the behavior of a simple lens, with a view to gain familiarity with lens systems. We use the ray concept to understand the behavior of light passing through lenses and derive the relationship between focal length of the lens, object distance and image distance.
Lens is mainly of two types- Convex lens and Concave lens. A convex lens is thicker at the center than at the edges while a concave lens is thinner at the center that at the edges. A convex lens is a converging lens since a parallel beam of light, after refraction, converges to a point, F. A concave lens is called a diverging lens since rays coming parallel to the principal axis, after refraction, diverge out and seem to come from a point, F”. Referred from Text Book of Optics by Dr. M.N.SUBRAHMANYAM, BRIJLAL, Dr. M.N.AVADHANULU, page no:- 71-72
Comparing the human eye and camera?
Video Courtesy – Youtube, Adam Kelsey
“The human eye is a wonderful instrument, relying on refraction and lenses to form images. There are many similarities between the human eye and a camera, including:
• A diaphragm to control the amount of light that gets through to the lens. This is the shutter in a camera, and the pupil, at the center of the iris, in the human eye.
• A lens to focus the light and create an image. The image is real and inverted.
• A method of sensing the image. In a camera, film is used to record the image; in the eye, the image is focused on the retina, and a system of rods and cones is the front end of an image-processing system that converts the image to electrical impulses and sends the information along the optic nerve to the brain”.
Referred from http://physics.bu.edu/~duffy/semester2/c29_eye.html
Why we cannot differentiate colors in dark places?
“There are two types of cells in our eyes that perceive light – rod cell and cone cell. Rods are sensitive to light intensity, but they cannot differentiate between different wavelengths of light. We can think of rods as seeing in black, white and shades of gray. Rods can’t distinguish the details of what we are looking at as well in low light condition. That is why when we are in a dark room and walking around at night colors seem much duller.
For our purpose, we are mainly interested in cone cells. Cones perceive greater details that rods, are sensitive to different wavelengths of light, and provide us with color vision, but they don’t work as well in low light as rods do. We have three different types of cone cells. Each of these cone cells is most responsive to light of different wavelengths. Together, they allow us to distinguish between different parts of the visible light spectrum and experience them as color.
A curious thing is that in dim light you can see more clearly out of the side of your eye, because the light-sensitive rods are more highly concentrated off to the side in the black of your eye”.
Referred from http://indianapublicmedia.org/amomentofscience/night-vision-humans-color/