Q. 5 3.9( 20 Votes )

When we enter a dark room coming from outside, immediately the things inside the room do not appear clear to our eyes. This is because
A. pupils do not open at all in the dark.

B. pupils take time to adjust.

C. light travels slower in a dark room.

D. pupils open very quickly in the dark.


The phenomena of light responsible for the working of the human eye is

i) reflection

ii) refraction

iii) power of accommodation

iv) persistence of vision

Answer :

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.


ii) Refraction

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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