A person wears glasses of power – 2.5 D. Is the person farsighted or nearsighted? What is the far point of the person without the glasses?

Sol. The person wears glasses of power –2.5D So, the person must be near sighted. u = ∞, v = far point, f = 1/-25 = - 0.4m = - 40 cm now, 1/v – 1/u = 1/f ⇒ 1/v = 1/u + 1/f = 0 + 1/-40 ⇒ v = - 40 cm So, the far point of the person is 40 cm