What type of spectacles should be worn by a person having the defect of myopia as well as hypermetropia? (ii) The far point of a myopic person is 150 cm. What is the nature and the power of lens required to correct the defect? (iii) With the help of ray diagrams, show the formation of image by (i) a myopic eye (ii) correction of myopic eye by using an appropriate lens.

What type of spectacles should be worn by a person having the defect o

1.	What type of spectacles should be worn by a person having the defect of myopia as well as hypermetropia? (ii) The far point of a myopic person is 150 cm. What is the nature and the power of lens required to correct the defect? (iii) With the help of ray diagrams, show the formation of image by (i) a myopic eye (ii) correction of myopic eye by using an appropriate lens.
Answer» Solution :(i) Spectacle having BIFOCAL lens. (ii) `u=oo, v=-150cm`. Using lens FORMULA, `(1)/(F)=(1)/(v)-(1)/(u)` `rArr""(1)/(f)=(1)/(-150)-(1)/(@) therefore f=-150cm`. `"POWER of lens " P=(1)/(f)=(-100)/(150)` `=0.67D` NATURE of lens : Concave. (iii)