Question

For a normal eye, the cornea of eye provides a converging power of 40 D and the least converging power of the eye lens behind the comes is 20 D. Using this information, the distance between the retina and the comea-eye lens can be estimated to be

• A. 5 cm
• B. 2.5 cm
• C. 1.67 cm
• D. 1.5 cm

Answer 1

The Correct Option is C

To solve this problem, we need to estimate the distance between the retina and the cornea-eye lens system, given the combined converging power of the cornea and the eye lens.

The power of a lens system in optics is given by the formula:

P = \frac{1}{f}

where P is the power in diopters (D), and f is the focal length in meters.

Given:

• Power of the cornea, P_c = 40 \, D
• Power of the eye lens, P_e = 20 \, D

The total power of the eye lens system is the sum of the powers of the cornea and the eye lens:

P_{total} = P_c + P_e = 40 \, D + 20 \, D = 60 \, D

Now, using the formula for power to find the focal length:

f = \frac{1}{P_{total}} = \frac{1}{60} \, \text{m} = 0.01667 \, \text{m}

Converting this focal length from meters to centimeters:

0.01667 \, \text{m} = 1.67 \, \text{cm}

Therefore, the distance between the retina and the cornea-eye lens system can be estimated to be 1.67 cm. Hence, the correct answer is:

1.67 cm