question_answer 23)

for a normal eye, the far point is at infinityand the near point of distinct vision is about 2.5 cm in front of the eye. The cornea of the eyeprovides a converging power of about 40dioptres, and the least converging power of theeye lens behind the cornea is about 20 dioptres. From this rough data estimate the range ofaccommodation (i.e., the range of converging power of the eye-lens) of a normal eye.  

Answer:

When the object is placed at infinity, the eyemakes use of the least converging power,Therefore, total converging power of corneaand the eye lens = 40 + 20 = 60 dioptre. Using i.e., To focus the object at the near point, or  Power dioptre = 64 dioptre Power of eye lens = 64 - 40 = 24 dioptre. Therefore, the rough range of eye lens is 20 to 24 dioptre.