The Near Point Of A Person Is 50cm And His Far Point Is 200cm. Can You Calculate Power Of Lenses Which Spectacles Should Have To See Clearly The Distant Objects?

Here are the calculations.
Here q = -200cm  ,     p = infinity.
Using lens formula
  1/f =  1/p + 1/q
  1/ f = 1/ infinity - 1/ 200cm  or F = -200cm = -2m
Power of lens = P = 1/f(m) = -1/2D = -0.5D.
     Thus for the correction of short sightedness, the person should use a concave lens of 0.5D power.