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Why must we hold a book about 25 cm away to read it comfortably?
AThe light reflected from the page is too bright (option)
BCloser than this, the eye cannot focus a sharp image on the retina
CThe book damages the retina
DThe optic nerve cannot reach closer light
Answer & Solution
Correct answer: B. Closer than this, the eye cannot focus a sharp image on the retina
1. 25 cm is the least distance of distinct vision for a normal adult eye.
2. Within this distance, the eye cannot accommodate sufficiently to bring the image to focus on the retina.
3. Holding the book at ~25 cm therefore minimises eye-strain while allowing sharp focus.
_Source: NCERT Class 10 Science, Ch 10 "The Human Eye and the Colourful World", §10.1.1_
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