LIGHT AND HUMAN EYE

LIGHT AND HUMAN EYE

                                                                             

1     Law of reflection

     1.    Angle of incidence is equal of angle of reflection

     2.    Incident ray , reflected ray and normal ray lie on same point

 Multiple images are formed when we put the object between two mirrors. The number of Image formed is depends on angle between the mirror.

                                       Number of Image =  360/Angle -1  

White light is a mixture of seven colour. When we pass the light through light disperse in seven original colour. Violet,Blue, Indigo, Green,Yellow,Orange,Red. 

HUMAN EYE

Cornea- The outer transparent part of eye under which Iris, lens etc lie.

Pupil- It allow light to enter in retina.  

Iris- It is part of eye which controls the amount of light enter in eye by controlling the pupil. It shrink when asses light enter in eye and it became expand when amount of light decrease. The colour of eye is nothing but the colour or lris.

Retina- it seems like screen where Image is formed.

Lens- It helps in converging the light on retina like projector.

Ciliary muscle- It control the lens and help the lens to form the Image on retina.

Optic nerve- It send the message of sight to the brain after that brain work on that information.

There are two types of cells

Rod cell - These are sensitive to dim light.

Cones cell- These are sensitive to bright light

Blind spot- At the junction of the optic nerve and the retina, there are no sensory cells, so no vision is possible at that spot. This is called the blind spot.

 Persistence of vision is 1/16. Our eye can see 16 images in one second.

The most comfortable distance at which one can read with a normal eye is about 25 cm.

Myopia- It is also called shortsightedness. In which person can see nearby object clearly but can’t see far object clearly.

Hypermetropia – It is also called farsightedness. In which person can see far object clearly but can’t see nearby clearly.   

                                                      

Sometimes, particularly in old age, eyesight becomes foggy. It is due to the eye lens becoming cloudy. When it happens, persons are said to have cataract.

       

Braille System

 This system is developed for visually challenged people this methods depend upon recognition by touching. Each character has to be memorised. Braille texts can be produced by hand or by machine. Type writer - like devices and printing machines have now been developed.

      

Point 11 and 12 are given for visually challenged people. They touch it and recognize the note.