Human eye and colourful world
Eye retina retains image on it for ______ of a second even after removal of object.
1/16th
Cornea of dead persons' eye is removed within ____ hours of death and transplanted in blind persons' eye.
6
_______ interprets these electrical signals.
Brain
A person using spectacles, contact lens or have been operated for cataract or suffering from hypertension can donate eyes. True / False
False
_____ is the distance of most distant point up to which a person can see object distinctly. It is_____ for normal vision.
Far point, infinity
______ is the most sensitive part of the eye that has nearly 70,000 sensitive cells which convey the electric impulses to the brain via ______.
Retina, optical nerve
____ present on the retina are sensitive to intensity of light and ______ are sensitive to colours of light.
Rods, cones
What are the defects of the eye?
The defects of the eye are myopia, hypermetropia, presbyopia, astigmatism, and colour blindness.
Eyes can be donated after death. State True / False
True
Redness of sky at sunrise or at sun set is due to ___________ .
atmospheric refraction
For curing presbyopia, ___________ are required.
bifocal lenses
Absence of all colours is ____ and presence of all in specific ratio is _____.
black, white
Colour blindness ______ be cured.
cannot
Focal length of eye lens can be varied with the help of _____
ciliary muscles
Colour of the iris determines the ______ of the eye.
colour
Hypermetropic person cured by using a ________ of suitable focal length.
convergent lens ( convex or convavo-convex)
Astigmatism is cured by using ______________.
cylindrical lens
Myopic person cured by using a ________ of suitable focal length.
divergent lens ( concave or convexo-concave)
Light sensitive cells get activated during illumination and produce ___________.
electrical signals
A ______ or _______ person can see far off objects clearly but cannot see near objects clearly.
hypermetropic, long sighted person
A person who cannot see far off objects clearly but can see near object clear is suffering from ______ or _______
myopia, short sightedness.
Eye is the most useful natural __________
optical instrument
The electrical signals are conveyed to the brain via ______.
optical nerves
Most sensitive part of the retina is called ________.
yellow spot