Question

The eye is a natural optical device by which humans can see the objects around them. It forms an inverted and real image on the retina, by the phenomenon of refraction of light through a natural convex lens. Sam is unable to read anything closer than 75 cm. His mother discussed the same with the doctor. The doctor explained this vision defect to her and told her how it is corrected.
B) The power prescribed by the doctor to see the newspaper clearly placed at 25 cm. ​

Answer 1

Given:
u = -25 cm; v = -75 cm
Step 1:Calculate ‘f’ using the lens formula:
1/v - 1/u = 1/f
1/(-75) - 1/(-25) = 1/f
1/f = 2/75 $c{m}^{-1}=8/3m^{-1}$
Step 2: Calculate Power
P = 1/f (in m)
P = 8/3 D = 2.67 D