Question

Eye is a natural optical device by which human could see the objects around him. It forms an inverted and real image on retina, through the phenomenon of refraction of light through a natural convex lens. Sam is unable to read anything closer than 75 cm. Her mother takes him to a doctor.
B) What power would the doctor prescribe him 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