Question

A person needs a lens of power-5.5 dioptres for correcting his distant vision. For
correcting his near vision he needs a lens of power +1.5 dioptre. What is the focal
length of the lens required for correcting (i) distant vision, and (ii) near vision?​

Answer 1

Answer:

(i) -0.18 m

(ii)0.67 m

Explanation:

(i) P = $\frac{1}{f}$  here f should be in metres

-5.5 = 1/f

therefore, f = - 0.18 m

(ii) P = $\frac{1}{f}$  

1.5 = 1/f (in metres)

therefore, f = + 0.67 m