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NEET PHYSICSMedium

For a normal eye, the cornea of eye provides a converging power of 40 D40\text{ D} and the least converging power of the eye lens behind the cornea is 20 D20\text{ D}. Using this information, the distance between the retina and the cornea-eye lens can be estimated to be:

A

5 cm

B

25 cm

C

1.67 cm

D

1.5 cm

Step-by-Step Solution

  1. Total Converging Power (PP): The effective power of the eye is the sum of the power of the cornea and the power of the eye lens (assuming they act as a combined lens system close to each other). P=Pcornea+PlensP = P_{cornea} + P_{lens} P=40 D+20 D=60 DP = 40\text{ D} + 20\text{ D} = 60\text{ D}.
  2. Focal Length (ff): The relationship between power (in Diopters) and focal length (in meters) is P=1fP = \frac{1}{f}.
  • f=1P=160 mf = \frac{1}{P} = \frac{1}{60}\text{ m}.
  1. Unit Conversion: Convert the focal length from meters to centimeters.
  • f=10060 cm=106 cm≈1.67 cmf = \frac{100}{60}\text{ cm} = \frac{10}{6}\text{ cm} \approx 1.67\text{ cm}.
  1. Distance to Retina: For a normal eye viewing a distant object (least converging power), the image forms on the retina. Therefore, the distance between the optical center of the eye system and the retina is equal to the focal length, which is approximately 1.67 cm1.67\text{ cm}.
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