Calculate Focal Length to Reduce Viewing Distance to 25cm

AI Thread Summary
To calculate the focal length of a converging lens needed to allow a patient to see objects at 25cm instead of 1m, the lensmaker's equation is applied. The initial attempt used the standard form of the equation but did not yield the correct result. The correct approach involves using the modified formula 1/u - 1/v = 1/f, where u is the object distance (1m) and v is the image distance (0.25m). The expected focal length is 33cm, indicating that the image formed is virtual. This calculation is crucial for aiding the patient's vision at closer distances.
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Homework Statement


A patient is unable to see objects closer than 1m from the eye. Calculate the focal length of the converging lens which is required to reduce this to 25cm.


Homework Equations



Lensmaker's equation: 1/u + 1/v = 1/f

u= distance from object to lens
v= distance of image to lens
f = focal length


The Attempt at a Solution



I tried using the above equation by substituting in u=1m, v=0.25m. But that doesn't help. The solution should be 33cm.
 
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Here the image is virtual.
So the formula should be
1/u - 1/v = 1/f.
 

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