Calculating Focal Length of Eye-Lens System

[vucollegeguy]

Homework Statement

a) What is the focal length of the eye-lens system when viewing an object at infinity? Assume that the lens-retina distance is 1.8cm.
b) What is the focal length of the eye-lens system when viewing an object 35cm from the eye? Assume that the lens-retina distance is 1.8cm .

Homework Equations

The Attempt at a Solution

I assumed that for part A that 1/inf went to zero but that answer was wrong. I'm not sure How to calculate this. Please help if you can.

 

[anathema]

Hello there,

Thank you for your question. The focal length of the eye-lens system can be calculated using the lens formula, which states that 1/f = 1/u + 1/v, where f is the focal length, u is the object distance and v is the image distance. In this case, the object distance is infinity (since the object is at infinity) and the image distance is equal to the lens-retina distance, which is given as 1.8cm. Therefore, the focal length can be calculated as f = 1/(1/u + 1/v) = 1/(1/inf + 1/1.8) = 1.8cm.

For part B, the object distance is 35cm and the image distance is still 1.8cm. Therefore, the focal length can be calculated as f = 1/(1/35 + 1/1.8) = 1.74cm.

I hope this helps. Let me know if you have any further questions. Keep up the good work!