A nearsighted person has a far point of 25.525.5cm and is prescribed contact lenses to correct her vision. What lens strength (a. k.a., lens power), in Diopters, should be prescribed

The right answer is "-3.90 D".

Explanation:

According to the question,

Far point,

v = -25.525 cm

and,

u =

By using the lens formula, we get

⇒

On putting the values, we get

⇒    

⇒  

or,

⇒    

hence,

⇒

⇒                      

⇒                  

grav potential energy

i don't understand. explain it clearly