Q. 53.9( 20 Votes )
The human retina relies on two types of photoreceptors for this phenomenon called dark adaptation. The cone cells, respond to light even high levels of illumination.
Rods are photoreceptors for night vision and work slowly when a person is entering from a brightly lit room to dimly lit room.
In the dark, the pupil dilates to let more light in.
Both these cells slowly increase their sensitivity to light in a dim environment. Cones adapt faster than the rod cells.
Refraction is the phenomenon responsible for image formation by the eye. The rays usually reach the eyes after reflecting off the surfaces. Refractive errors that occur are imperfections which prevent the proper working of the eye and can be rectified using proper lenses or sometimes by surgical methods.
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(a) Draw ray diagrams showing the image formation by a convex lens when an object is placed
(i) at twice the focal length of the lens
(ii) at infinity
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