A doctor prescribes a corrective lens of power -0.5 D to a person. Find the focal length of the lens. Is this lens diverging or converging? Give reason. How does the property of this lens can be used to correct eye defects ?

A doctor prescribes a corrective lens of power -0.5 D to a person. Fin

1.	A doctor prescribes a corrective lens of power -0.5 D to a person. Find the focal length of the lens. Is this lens diverging or converging? Give reason. How does the property of this lens can be used to correct eye defects ?
Answer» SOLUTION :(i) He is suffering from myopia because the focal length required for the lens is negative. (ii) GIVEN P = -1.2 D. `F = (1)/(p_(1))` [where, P = power of lens and f = focal length] `= (1)/(-1.2) = -0.83 m`. (iii) The lens is diverging because power is negative. Or Given, Power (P) = = -0.5 D, Focal length (f) = ? `p = (1)/(f)rArr f = (1)/(P) rArr f = -(1)/(0.5) = 2m`. * This lens is diverging. * Because power of a lens is negative means the given lens is concave. * The diverging property of the lens is used to correct myopia. In myopic eye the image of a distant object is formed in front of the retina and not on the retina. * A concave lens of SUITABLE power diverges the light rays and brings the image back on the retina.